Exposure method, exposure apparatus, and device manufacturing method

ABSTRACT

Within area where of four heads installed on a wafer stage, heads included in the first head group and the second head group to which three heads each belong that include one head different from each other face the corresponding areas on a scale plate, the wafer stage is driven based on positional information which is obtained using the first head group, as well as obtain the displacement (displacement of position, rotation, and scaling) between the first and second reference coordinate systems corresponding to the first and second head groups using the positional information obtained using the first and second head groups. By using the results and correcting measurement results obtained using the second head group, the displacement between the first and second reference coordinate systems is calibrated, which allows the measurement errors that come with the displacement between areas on scale plates where each of the four heads face.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application is a divisional application ofNon-Provisional application Ser. No. 13/944,397 (now U.S. Pat. No.8,842,278), filed Jul. 17, 2013, which is a continuation application ofNon-Provisional application Ser. No. 12/860,097 (now U.S. Pat. No.8,514,395) filed Aug. 20, 2010, which claims the benefit of ProvisionalApplication No. 61/236,704 filed Aug. 25, 2009, the disclosure of whichis hereby incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to exposure methods, exposure apparatuses,and device manufacturing methods, and more particularly to an exposuremethod and an exposure apparatus used in a lithography process tomanufacture microdevices (electronic devices) such as a semiconductordevice, and a device manufacturing method using the exposure method orthe exposure apparatus.

2. Description of the Background Art

Conventionally, in a lithography process for manufacturing electrondevices (microdevices) such as semiconductor devices (such as integratedcircuits) and liquid crystal display devices, exposure apparatuses suchas a projection exposure apparatus by a step-and-repeat method (aso-called stepper), or a projection exposure apparatus by astep-and-scan method (a so-called scanning stepper (which is also calleda scanner) is mainly used.

In these types of exposure apparatuses, with finer device patterns dueto higher integration of semiconductor devices, requirements for highoverlay accuracy (alignment accuracy) is increasing. Therefore,requirements for higher accuracy is increasing, also in positionmeasurement of substrates such as a wafer and the like on which apattern is formed.

As an apparatus to meet such requirements, for example, in U.S. PatentApplication Publication No. 2006/0227309, an exposure apparatus isproposed which is equipped with a position measurement system using aplurality of encoder type sensors (encoder heads) installed on asubstrate table. In this exposure apparatus, the encoder head irradiatesa measurement beam on a scale which is placed facing a substrate table,and measures the position of the substrate table by receiving a returnbeam from the scale. In the position measurement system disclosed inU.S. Patent Application Publication No. 2006/0227309 and the like, it isdesirable for the scale to cover as much movement area of the substratetable as possible, except for the area right under the projectionoptical system. Therefore, a scale with a large area becomes necessary;however, to make a highly precise scale having a large area is verydifficult, as well as costly. Accordingly, a plurality of small-areascales are usually made which is the scale divided into a plurality ofsections, and then the small-scales are combined. Accordingly, while itis desirable for the alignment performed on the plurality of scales tobe accurate, it is difficult in reality to make a scale with noindividual difference, and to put the scales together without anyerrors.

SUMMARY OF THE INVENTION

The present invention was made under the circumstances described above,according to a first aspect, there is provided a first exposure methodin which an object is exposed, the method comprising: obtainingcorrection information in a first movement area of a movable body whereof a plurality of heads provided on the movable body which moves along apredetermined plane, a plurality of head groups to which a plurality ofheads including at least one head different from each other belong facesa measurement plane placed roughly parallel to the predetermined planeoutside of the movable body, the correction information beinginformation of a displacement between a plurality of different referencecoordinate systems corresponding to each of the plurality of headgroups; and exposing an object held by the movable body by obtainingpositional information of the movable body using a plurality of headsbelonging to the plurality of head groups, and driving the movable bodyusing the positional information and the correction information of thedisplacement between the plurality of different reference coordinatesystems corresponding to the plurality of head groups within the firstmovement area.

According to this method, it becomes possible to drive the movable bodywith good precision within the first movement area using the positionalinformation of the movable body obtained using a plurality of headscorresponding to each of a plurality of head groups, without beingaffected by displacement between a plurality of different referencecoordinate system corresponding to each of the plurality of head groups,which makes exposure with high precision possible to the object held bythe movable body.

According to a second aspect of the present invention, there is provideda second exposure method in which an object is exposed, the methodcomprising: driving a movable body within a predetermined area where ofa first number of heads installed on the movable body holding theobject, a second number of heads belonging to a first head group and asecond head group including at least one head different from each otherface a corresponding area on a measurement plane, based on at least oneof a first and second positional information which is obtained using thefirst and second head groups to expose the object.

According to this method, it becomes possible to drive the movable bodywith high precision even if the coordinate systems corresponding to thefirst head group and the second head group differ, without beingaffected.

According to a third aspect of the present invention, there is provideda first exposure apparatus which exposes an object, the apparatuscomprising: a movable body which holds an object and moves along apredetermined plane; a position measurement system which obtainspositional information of the movable body based on an output of a headwhich irradiates a measurement beam on a measurement plane placedroughly parallel to the predetermined plane external to the movable bodyin the vicinity of an exposure position to the object, and receives areturn beam from the measurement plane, of a plurality of heads providedon the movable body; and a control system which drives the movable bodybased on the positional information obtained by the position measurementsystem, and switches a head which the position measurement system usesto obtain the positional information out of the plurality of headsaccording to the position of the movable body, wherein the controlsystem corrects a displacement between a plurality of referencecoordinate systems reciprocally corresponding to the plurality of heads,within a first movement area of the movable body where the plurality ofheads face the measurement plane.

According to this apparatus, because reciprocal displacement of theplurality of reference coordinate systems is corrected, it becomespossible to measure the positional information of the movable body anddrive (control the position of) the movable body with high precisionusing the plurality of heads.

According to a fourth aspect of the present invention, there is provideda second exposure apparatus which exposes an object, the apparatuscomprising: a movable body which holds the object and moves along apredetermined plane; a position measurement system which obtainspositional information of the movable body based on an output of a headwhich irradiates a measurement beam on a measurement plane placedroughly parallel to the predetermined plane external to the movable bodyin the vicinity of an exposure position to the object, and receives areturn beam from the measurement plane, of a first number of headsinstalled on the movable body; a drive system which drives the movablebody; and a control system which controls the drive system within apredetermined area where of a first number of heads of the positionmeasurement system, a second number of heads belonging to a first headgroup and a second head group including at least one head different fromeach other face a corresponding area on a measurement plane, based on atleast one of a first and second positional information which is obtainedusing the first and second head groups.

According to this apparatus, it becomes possible to drive the movablebody with high precision even if the coordinate systems corresponding tothe first head group and the second head group differ, without beingaffected.

According to a fifth aspect of the present invention, there is provideda third exposure apparatus which exposes an object, the apparatuscomprising: a movable body which holds the object and moves along apredetermined plane; a position measurement system which obtainspositional information of the movable body based on an output of a headwhich irradiates a measurement beam on a measurement plane placedroughly parallel to the predetermined plane external to the movable bodyin the vicinity of an exposure position to the object, and receives areturn beam from the measurement plane, of a plurality of heads providedon the movable body; and a control system which drives the movable bodybased on the positional information obtained by the position measurementsystem, as well as obtains a correction information of the positionalinformation of the movable body obtained by the position measurementsystem by moving the movable body within an area where positionmeasurement can be performed using a second number of heads which ismore than a first number of heads which are used in position control ofthe movable body.

According to this apparatus, because correction information of thepositional information of the movable body obtained by the positionmeasurement system is obtained by the control system, it becomespossible to drive the movable body with high precision, using thecorrection information.

According to a sixth aspect of the present invention, there is provideda third exposure method in which an object is exposed, the methodcomprising: obtaining a correction information of a positionalinformation of the movable body obtained by a position measurementsystem by moving the movable body within a first movement area of themovable body in which of a plurality of heads provided on a movable bodywhich moves along a predetermined plane, a plurality of group heads towhich a first number of heads that are required to control the positionof the movable body including at least head one different with eachother belong, faces a measurement plane place roughly in parallel to thepredetermined plane outside of the movable body; and exposing the objectholding the movable body by driving the movable body using thecorrection information.

According to this method, exposure to the object with high precisionbecomes possible.

According to a seventh aspect of the present invention, there isprovided a fourth exposure apparatus which exposes an object, theapparatus comprising: a movable body which holds the object and movesalong a predetermined plane; a position measurement system which obtainspositional information of the movable body based on an output of a headwhich irradiates a measurement beam on a measurement plane made up of aplurality of scale plates that is placed roughly parallel to thepredetermined plane external to the movable body in the vicinity of anexposure position to the object, and receives a return beam from themeasurement plane, of a plurality of heads provided on the movable body;and a control system which drives the movable body based on thepositional information obtained by the position measurement system, andswitches a head which the position measurement system uses to obtain thepositional information out of the plurality of heads according to theposition of the movable body, wherein the control system obtains apositional relation between a plurality of scale plates reciprocallycorresponding to the plurality of heads, within a first movement area ofthe movable body where the plurality of heads face the measurementplane.

According to the apparatus, because the positional relation between theplurality of scale plates reciprocally is obtained by the controlsystem, it becomes possible to measure the positional information of themovable body using the plurality of heads and also drive (control theposition of) the movable body with high precision.

According to an eighth aspect of the present invention, there isprovided a fourth exposure method in which an object is exposed, themethod comprising: obtaining a positional relation in a first movementarea of a movable body where of a plurality of heads provided on themovable body which moves along a predetermined plane, a plurality ofhead groups to which a plurality of heads including at least one headdifferent from each other belong faces a measurement plane made up ofthe plurality of scale plates placed roughly in parallel with thepredetermined plane outside of the movable body, the positional relationbeing a relation between the plurality of scale plates reciprocallycorresponding to each of a plurality of head groups; and exposing anobject held by the movable body by obtaining positional information ofthe movable body using a plurality of heads corresponding to theplurality of head groups, and driving the movable body using thepositional information and the positional relation between the pluralityof scale plates reciprocally corresponding to each of the plurality ofhead groups within the first movement area.

According to this method, it becomes possible to drive the movable bodywith good precision within the first movement area using the positionalinformation of the movable body obtained using a plurality of headscorresponding to each of a plurality of head groups, without beingaffected by a positional displacement between a plurality of scaleplates corresponding to each of the plurality of head groups, whichmakes exposure with high precision possible to the object held by themovable body.

According to a ninth aspect of the present invention, there is provideda device manufacturing method, including exposing an object using anyone of the first to fourth exposure apparatuses of the presentinvention, and forming a pattern on the object; and developing theobject on which the pattern is formed.

According to a tenth aspect of the present invention, there is provideda device manufacturing method, including exposing an object using anyone of the first to fourth exposure methods of the present invention,and forming a pattern on the object; and developing the object on whichthe pattern is formed.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings;

FIG. 1 is a view schematically showing the configuration of an exposureapparatus related to an embodiment;

FIG. 2 is a view showing a configuration of an encoder system placed inthe periphery of a projection optical system;

FIG. 3 is a view showing a configuration of an encoder system placed inthe periphery of an alignment system;

FIG. 4 is an enlarged view of a wafer stage partially fractured;

FIG. 5 is a view showing a placement of encoder heads on the waferstage;

FIG. 6 is a block diagram showing the main configuration of the controlsystem related with the stage control in the exposure apparatus in FIG.1;

FIG. 7A is a view showing a relation between a placement of encoderheads and a scale plate and a measurement area of the encoder system,FIG. 7B is a view showing four stage coordinate systems which are setcorresponding to four sets of encoder heads facing the scale plate, andFIG. 7C is a view showing a case when there is a displacementreciprocally in the four sections of the scale plate;

FIGS. 8A, 8C, and 8E are views (Nos. 1, 2, and 3) showing a movement ofthe wafer stage in stage position measurement to calibrate a stagecoordinate, and FIGS. 8B, 8D, and 8F are views (Nos. 1, 2, and 3) usedto explain calibration of the four stage coordinate systems (the one ortwo and 3);

FIGS. 9A and 9B are views used to explain an origin, rotation, andmeasurement of scaling of combined stage coordinate system C_(E); and

FIGS. 10A and 10B are views used to explain an origin, rotation, andmeasurement of scaling of combined stage coordinate system C_(A).

DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present invention will be described below, withreference to FIGS. 1 to 10B.

FIG. 1 schematically shows the configuration of an exposure apparatus100 related to the present embodiment. Exposure apparatus 100 is aprojection exposure apparatus of the step-and-scan method, namely theso-called scanner. As it will be described later, a projection opticalsystem PL is arranged in the embodiment, and in the description below, adirection parallel to an optical axis AX of projection optical system PLwill be described as the Z-axis direction, a direction within a planeorthogonal to the Z-axis direction in which a reticle and a wafer arerelatively scanned will be described as the Y-axis direction, adirection orthogonal to the Z-axis and the Y-axis will be described asthe X-axis direction, and rotational (inclination) directions around theX-axis, the Y-axis, and the Z-axis will be described as θ x, θ y, and θz directions, respectively.

Exposure apparatus 100 is equipped with an illumination system 10, areticle stage RST holding reticle R, a projection unit PU, a wafer stagedevice 50 including wafer stages WST1 and WST2 on which a wafer W ismounted, a control system for these parts and the like.

Illumination system 10 includes a light source, an illuminanceuniformity optical system, which includes an optical integrator and thelike, and an illumination optical system that has a reticle blind andthe like (none of which are shown), as is disclosed in, for example,U.S. Patent Application Publication No. 2003/0025890 and the like.Illumination system 10 illuminates a slit-shaped illumination area IAR,which is set on reticle R with a reticle blind (a masking system), by anillumination light (exposure light) IL with a substantially uniformilluminance. Here, as one example, ArF excimer laser light (with awavelength of 193 nm) is used as the illumination light IL.

On reticle stage RST, reticle R on which a circuit pattern or the likeis formed on its pattern surface (the lower surface in FIG. 1) is fixed,for example, by vacuum chucking. Reticle stage RST is finely drivablewithin an XY plane, for example, by a reticle stage drive section 11(not shown in FIG. 1, refer to FIG. 6) that includes a linear motor orthe like, and reticle stage RST is also drivable in a scanning direction(in this case, the Y-axis direction, which is the lateral direction ofthe page surface in FIG. 1) at a predetermined scanning speed.

The positional information (including position information in the θzdirection (θz rotation quantity)) of reticle stage RST in the XY plane(movement plane) is constantly detected, for example, at a resolution ofaround 0.25 nm by a reticle laser interferometer (hereinafter referredto as a “reticle interferometer”) 16, which irradiates a measurementbeam on a movable mirror 15 (the mirrors actually arranged are a Ymovable mirror (or a retro reflector) that has a reflection surfacewhich is orthogonal to the Y-axis direction and an X movable mirror thathas a reflection surface orthogonal to the X-axis direction) shown inFIG. 1. Incidentally, to measure the positional information of reticle Rat least in directions of three degrees of freedom, instead of, ortogether with reticle interferometer 16, the encoder system which isdisclosed in, for example, U.S. Patent Application Publication No.2007/0288121 and the like can be used.

Projection unit PU is placed below (−Z side) reticle stage RST in FIG.1, and is held by a main frame (not shown) (metrology frame) whichconfigures a part of a body. Projection unit PU has a barrel 40, and aprojection optical system PL consisting of a plurality of opticalelements held by barrel 40. As projection optical system PL, forexample, a dioptric system is used, consisting of a plurality of lenses(lens elements) that has been disposed along optical axis AX, which isparallel to the Z-axis direction. Projection optical system PL is, forexample, a both-side telecentric dioptric system that has apredetermined projection magnification (such as one-quarter, one-fifth,or one-eighth times). Therefore, when illumination light IL fromillumination system 10 illuminates illumination area IAR, illuminationlight IL that has passed through reticle R which is placed so that itspattern surface substantially coincides with a first plane (an objectplane) of projection optical system PL forms a reduced image of thecircuit pattern (a reduced image of a part of the circuit pattern) ofreticle R formed within illumination area IAR, via projection opticalsystem PL, in an area (exposure area) IA conjugate to illumination areaIAR on wafer W whose surface is coated with a resist (a sensitive agent)and is placed on a second plane (an image plane) side of projectionoptical system PL. And by reticle stage RST and wafer stages WST1 andWST2 being synchronously driven, reticle R is relatively moved in thescanning direction (the Y-axis direction) with respect to illuminationarea IAR (illumination light IL) while wafer W is relatively moved inthe scanning direction (the Y-axis direction) with respect to exposurearea IA (illumination light IL), thus scanning exposure of a shot area(divided area) on wafer W is performed, and the pattern of reticle R istransferred onto the shot area. That is, in the embodiment, the patternof reticle R is generated on wafer W according to illumination system 10and projection optical system PL, and then by the exposure of thesensitive layer (resist layer) on wafer W with illumination light IL,the pattern is formed on wafer W.

Incidentally, the main frame can be one of a gate type frame which isconventionally used, and a hanging support type frame disclosed in, forexample, U.S. Patent Application Publication No. 2008/0068568 and thelike.

In the periphery on the −Z side end of barrel 40, for example, a scaleplate 21 is placed parallel to the XY plane, at a height substantiallyflush with a surface on the lower end of barrel 40. As shown in FIG. 2in the embodiment, scale plate 21 is configured, for example, of fourL-shaped sections (parts) 21 ₁, 21 ₂, 21 ₃, and 21 ₄, and the −Z end ofbarrel 40 is inserted, for example, inside a rectangular shaped opening21 a formed in the center. In this case, the width in the X-axisdirection and the Y-axis direction of scale plate 21 is a and b,respectively, and the width of opening 21 a in the X-axis direction andthe Y-axis direction is a_(i) and b_(i), respectively.

At a position away from scale plate 21 in the +X direction is a scaleplate 22, which is placed substantially flush with scale plate 21, asshown in FIG. 1. Scale plate 22 is also configured, for example, of fourL-shaped sections (parts) 22 ₁, 22 ₂, 22 ₃, and 22 ₄ as is shown in FIG.3, and the −Z end of an alignment system ALG which will be describedlater is inserted, for example, inside a rectangular shaped opening 22 aformed in the center. The width in the X-axis direction and the Y-axisdirection of scale plate 22 is a and b, respectively, and the width ofopening 22 a in the X-axis direction and the Y-axis direction is a_(i)and b_(i), respectively. Incidentally, in the embodiment, while thewidth of scale plates 21 and 22, and the width of openings 21 a and 22 ain the X-axis and the Y-axis directions were the same, the width doesnot necessarily have to be the same, and the width may differ in atleast one of the X-axis and the Y-axis directions.

In the embodiment, scale plates 21 and 22 are supported by suspensionfrom a main frame (not shown) (metrology frame) which supportsprojection unit PU and alignment system ALG. On the lower surface (asurface on the −Z side) of scale plates 21 and 22, a reflection typetwo-dimensional diffraction grating RG (refer to FIGS. 2, 3, and 4) isformed, consisting of a grating of a predetermined pitch, such as, forexample, a grating of 1 μm whose periodic direction is in a direction of45 degrees with the X-axis serving as a reference (a direction of −45degrees when the Y-axis serves as a reference), and a grating of apredetermined pitch, such as, for example, a grating of 1 μm, whoseperiodic direction is in a direction of −45 degrees with the X-axisserving as a reference (−135 degrees when the Y-axis serves as areference). However, due to the configuration of the two-dimensionalgrating RG and an encoder head which will be described later on, anon-effective area having a width t is included in each of the vicinityof the outer periphery of sections 21 ₁ to 21 ₄ and 22 ₁ to 22 ₄configuring scale plates 21 and 22. The two-dimensional grating RG ofscale plates 21 and 22 covers a movement range of wafer stages WST1 andWST2, respectively, at least at the time of exposure operation andalignment (measurement).

Wafer stage device 50, as shown in FIG. 1, is equipped with a stage base12 supported almost horizontally by a plurality of (for example, threeor four) vibration isolation mechanisms (omitted in the drawings) on thefloor surface, wafer stages WST1 and WST2 placed on stage base 12, awafer stage drive system 27 (only a part of the system shown in FIG. 1,refer to FIG. 6) which drives wafer stages WST1 and WST2, and ameasurement system which measures the position of wafer stages WST1 andWST2 and the like. The measurement system is equipped with encodersystems 70 and 71, and a wafer laser interferometer system (hereinaftersimply described as a wafer interferometer system) 18 and the like shownin FIG. 6. Incidentally, encoder systems 70 and 71, and waferinterferometer system 18 will be further described later in thedescription. However, in the embodiment, wafer interferometer system 18does not necessarily have to be provided.

As shown in FIG. 1, stage base 12 is made of a member having a tabularform, and the degree of flatness of the upper surface is extremely highand serves as a guide surface when wafer stages WST1 and WST2 move.Inside stage base 12, a coil unit is housed, including a plurality ofcoils 14 a placed in the shape of a matrix with the XY two-dimensionaldirection serving as a row direction and a column direction.

Incidentally, another base member to support the base by levitation canbe provided separately from base 12, and stage base 12 can be made tofunction as a counter mass (reaction force canceller) which movesaccording to the law of conservation of momentum by the reaction forceof the drive force of wafer stages WST1 and WST2.

As shown in FIG. 1, wafer stage WST1 has a stage main section 91, and awafer table WTB1 which is placed above stage main section 91 and issupported in a non-contact manner with respect to stage main section 91by a Z tilt drive mechanism (not shown). In this case, wafer table WTB1is supported in a non-contact manner by Z tilt drive mechanism byadjusting the balance of the upward force (repulsion) such as theelectromagnetic force and the downward force (gravitation) including theself-weight at three points, and is also finely driven at least indirections of three degrees of freedom, which are the Z-axis direction,the ex direction, and the θy direction. At the bottom of stage mainsection 91, a slider section 91 a is arranged. Slider section 91 a has amagnetic unit made up of a plurality of magnets arrangedtwo-dimensionally within the XY plane, a housing to house the magneticunit, and a plurality of air bearings arranged in the periphery of thebottom surface of the housing. The magnet unit configures a planar motor30 which uses the drive of an electromagnetic force (the Lorentz force)as disclosed in, for example, U.S. Pat. No. 5,196,745, along with thecoil unit previously described. Incidentally, as planar motor 30, thedrive method is not limited the Lorentz force drive method, and a planarmotor by a variable reluctance drive system can also be used.

Wafer stage WST1 is supported by levitation above stage base 12 by apredetermined clearance (clearance gap/distance/gap/spatial distance),such as around several μm, by the plurality of air bearings describedabove, and is driven in the X-axis direction, the Y-axis direction, andthe θz direction by planar motor 30. Accordingly, wafer table WTB1(wafer W) is drivable with respect to stage base 12 in directions of sixdegrees of freedom (hereinafter shortly described as the X-axisdirection, the Y-axis direction, the Z-axis direction, the θx direction,the θy direction, and the θz direction (hereinafter shortly referred toas X, Y, Z, θx, θy, θz)).

In the embodiment, a main controller 20 controls the magnitude anddirection of current supplied each of the coils 14 a configuring thecoil unit. Wafer stage drive system 27 is configured, including planarmotor 30 and the Z tilt drive mechanism previously described.Incidentally, planar motor 30 is not limited to a motor using a movingmagnet method, and can be a motor using a moving coil method. Further,as planar motor 30, a magnetic levitation type planar motor can be used.In this case, the air bearing previously described does not have to bearranged. Further, wafer stage WST can be driven in directions of sixdegrees of freedom by planar motor 30. Further, wafer table WTB1 can bemade finely movable in at least one of the X-axis direction, the Y-axisdirection, and the θZ direction. More specifically, wafer stage WST1 canbe configured by a rough/fine movement stage.

On wafer table WTB1, wafer W is mounted via a wafer holder (not shown),and is fixed by a chuck mechanism (not shown), such as, for example,vacuum suction (or electrostatic adsorption). Further, on one of thediagonal lines on wafer table WTB1, a first fiducial mark plate FM1 anda second fiducial mark plate FM2 are provided, with the wafer holder inbetween (for example, refer to FIG. 2). On the upper surface of thefirst fiducial mark plate FM1 and the second fiducial mark plate FM2, aplurality of reference marks which are detected by a pair of reticlealignment systems 13A and 13B and alignment system ALG are formed,respectively. Incidentally, the positional relation between theplurality of reference marks on the first and second fiducial plates FM1and FM2 are to be known.

Wafer stage WST2 is also configured in a similar manner as wafer stageWST1.

Encoder systems 70 and 71 obtain (measure) positional information ofwafer stages WST1 and WST2, respectively, in directions of six degreesof freedom (X, Y, Z, θ x, θ y, θ z) in an exposure time movement area(in an area where the wafer stage moves when exposing a plurality ofshot areas on wafer W) including an area right below projection opticalsystem PL, and in an measurement time movement area including an arearight below alignment system ALG. Now, a configuration and the like ofencoder systems 70 and 71 will be described in detail. Incidentally,exposure time movement area (a first movement area) is an area in whichthe wafer stage moves during an exposure operation within the exposurestation (a first area) where the exposure of the wafer is performed viaprojection optical system PL, and the exposure operation, for example,includes not only exposure of all of the shot areas on the wafer towhich the pattern should be transferred, but also the preparatoryoperations (for example, detection of the fiducial marks previouslydescribed) for exposure. Measurement time movement area (a secondmovement area) is an area in which the wafer stage moves during ameasurement operation within the measurement station (a second area)where the measurement of the positional information is performed bydetection of alignment marks on the wafer by alignment system ALG, andthe measurement operation, for example, includes not only detection of aplurality of alignment marks on the wafer, but also detection(furthermore, measurement of positional information (step information)of the wafer in the Z-axis direction) of fiducial marks by alignmentsystem ALG.

In wafer tables WTB1 and WTB2, as shown in an planar view in FIGS. 2 and3, respectively, encoder heads (hereinafter appropriately referred to asa head) 60 ₁ to 60 ₄ are placed in each of the four corners on the uppersurface. In this case, the separation distance in the X-axis directionbetween heads 60 ₁ and 60 ₂ and the separation distance in the X-axisdirection between heads 60 ₃ and 60 ₄ are both equal to A. Further, theseparation distance in the Y-axis direction between heads 60 ₁ and 60 ₄and the separation distance in the Y-axis direction between heads 60 ₂and 60 ₃ are both equal to B. These separation distances A and B arelarger than width a_(i) and b_(i) of opening 21 a of scale plate 21.Specifically, taking into consideration width t of the non-effectivearea previously described, A≧a_(i)+2t, B≧b_(i)+2t. Heads 60 ₁ to 60 ₄are housed, respectively, inside holes of a predetermined depth in theZ-axis direction which have been formed in wafer tables WTB1 and WTB2 asshown in FIG. 4, with head 60 ₁ taken up as a representative.

As shown in FIG. 5, head 60 ₁ is a two-dimensional head in a −135degrees direction with the X-axis serving as a reference (in otherwords, a −45 degrees direction with the X-axis serving as a reference)and whose measurement direction is in the Z-axis direction. Similarly,heads 60 ₂ to 60 ₄ are two-dimensional heads that are in a 225 degreesdirection with the X-axis serving as a reference (in other words, a 45degrees direction with the X-axis serving as a reference) whosemeasurement direction is in the Z-axis direction, a 315 degreesdirection with the X-axis serving as a reference (in other words, a −45degrees direction with the X-axis serving as a reference) whosemeasurement direction is in the Z-axis direction, and a 45 degreesdirection with the X-axis serving as a reference whose measurementdirection is in the Z-axis direction, respectively. As is obvious fromFIGS. 2 and 4, heads 60 ₁ to 60 ₄ irradiate a measurement beam on thetwo dimensional diffraction grating RG formed on the surface of sections21 ₁ to 21 ₄ of scale plate 21 or sections 22 ₁ to 22 ₄ of scale plate22 that face the heads, respectively, and by receiving thereflected/diffraction beams from two-dimensional grating RG, measure theposition of wafer table WTB1 and WTB2 (wafer stages WST1 and WST2) foreach of the measurement directions. Now, as each of the heads 60 ₁ to 60₄, a sensor head having a configuration similar to a sensor head formeasuring variation as is disclosed in, for example, U.S. Pat. No.7,561,280, can be used.

In heads 60 ₁ to 60 ₄ configured in the manner described above, sincethe optical path lengths of the measurement beams in air are extremelyshort, the influence of air fluctuation can mostly be ignored. However,in the embodiment, the light source and a photodetector are arrangedexternal to each head, or more specifically, inside (or outside) stagemain section 91, and only the optical system is arranged inside of eachhead. And the light source, the photodetector, and the optical systemare optically connected via an optical fiber (not shown). In order toimprove the positioning precision of wafer table WTB (fine movementstage), air transmission of a laser beam and the like can be performedbetween stage main section 91 (rough movement stage) and wafer table WTB(fine movement stage) (hereinafter shortly referred to as a rough/finemovement stage), or a configuration can be employed where a head isprovided in stage main section 91 (rough movement stage) so as tomeasure a position of stage main section 91 (rough movement stage) usingthe head and to measure relative displacement of the rough/fine movementstage with another sensor.

When wafer stages WST1 and WST2 are located within the exposure timemovement area previously described, head 60 ₁ configures two-dimensionalencoders 70 ₁ and 71 ₁ (refer to FIG. 6) which irradiate a measurementbeam (measurement light) on (section 21 ₁ of) scale plate 21, receivethe diffraction beam from the grating whose periodical direction is in a135 degrees direction with the X-axis serving as a reference, or inother words, in a −45 degrees direction (hereinafter simply referred toas a −45 degrees direction) with the X-axis serving as a reference,formed on the surface (lower surface) of scale plate 21, and measure theposition of wafer tables WTB1 and WTB2 in the −45 degrees direction andin the Z-axis direction. Similarly, heads 60 ₂ to 60 ₄ each configuretwo-dimensional encoders 70 ₂ to 70 ₄ and 71 ₂ to 71 ₄ (refer to FIG. 6)which irradiate a measurement beam (measurement light) on (sections 21 ₂to 21 ₄ of) scale plate 21, respectively, receive a diffraction beamfrom the grating whose periodical direction is in a 225 degreesdirection, or in other words, in a +45 degrees direction (hereinaftersimply referred to as a 45 degrees direction), a 315 degrees direction,or in other words, whose periodical direction is in a −45 degreesdirection with the X-axis serving as a reference, and a 45 degreesdirection with the X-axis serving as a reference, formed on the surface(lower surface) of scale plate 21, and measure the position in the 225degrees (45 degrees) direction and in the Z-axis direction, the positionin the 315 degrees (−45 degrees) direction and the Z-axis direction, andthe position in the 45 degrees direction and the Z-axis direction ofwafer tables WTB1 and WTB2.

Further, when wafer stage WST1 and WST2 are located within themeasurement time movement area previously described, head 60 ₁configures two-dimensional encoders 70 ₁ and 71 ₁ (refer to FIG. 6)which irradiate a measurement beam (measurement light) on (section 22 ₁of) scale plate 22, receive the diffraction beam from the grating whoseperiodical direction is in a 135 degrees direction (−45 degreesdirection) with the X-axis serving as a reference formed on the surface(lower surface) of scale plate 22, and measure the position of wafertables WTB1 and WTB2 in the −45 degrees direction and in the Z-axisdirection. Similarly, heads 60 ₂ to 60 ₄ configure two-dimensionalencoders 70 ₂ to 70 ₄ and 71 ₂ to 71 ₄ (refer to FIG. 6) which irradiatea measurement beam (measurement light) on (sections 22 ₂ to 22 ₄ of)scale plate 22, respectively, receive a diffraction beam from thegrating whose periodical direction is in a 225 degrees direction (45degrees direction), a 315 degrees direction (−45 degrees direction), anda 45 degrees direction with the X-axis serving as a reference, formed onthe surface (lower surface) of scale plate 22, and measure the positionin the 225 degrees direction (45 degrees direction) and in the Z-axisdirection, the position in the 315 degrees direction (−45 degreesdirection) and the Z-axis direction, and the position in the 45 degreesdirection and the Z-axis direction of wafer tables WTB1 and WTB2.

As it can be seen from the description above, in this embodiment,regardless of irradiating the measurement beam (measurement light)either on scale plate 21 or 22, or in other words, regardless of whetherwafer stages WST1 and WST2 are located in the exposure time movementarea or the measurement time movement area, heads 60 ₁ to 60 ₄ configuretwo-dimensional encoder 70 ₁ to 70 ₄ along with the scale plates onwhich the measurement beam (measurement light) is irradiated, and heads60 ₁ to 60 ₄ on wafer stage WST2 are to configure two-dimensionalencoders 71 ₁ to 71 ₄, along with the scale plates on which themeasurement beams (measurement lights) are irradiated.

The measurement values of each of the two-dimensional encoders(hereinafter shortly referred to as an encoder as appropriate) 70 ₁ to70 ₄, and 71 ₁ to 71 ₄ are supplied to main controller 20 (refer to FIG.6). Main controller 20 obtains the positional information of wafer tableWTB1 and WTB2 within the exposure time movement area including the arearight under projection optical system PL, based on the measurementvalues of at least three encoders (in other words, at least threeencoders that output effective measurement values) which face the lowersurface of (sections 21 ₁ to 21 ₄ configuring) scale plate 21 on whichthe two-dimensional diffraction grating RG is formed. Similarly, maincontroller 20 obtains the positional information of wafer table WTB1 andWTB2 within the measurement time movement area including the area rightunder alignment system ALG, based on the measurement values of at leastthree encoders (in other words, at least three encoders that outputeffective measurement values) which face the lower surface of (sections22 ₁ to 22 ₄ configuring) scale plate 22 on which the two-dimensionaldiffraction grating RG is formed.

Further, in exposure apparatus 100 of the embodiment, the position ofwafer stages WST1 and WST2 (wafer tables WTB1 and WTB2) can be measuredwith wafer interferometer system 18 (refer to FIG. 6), independentlyfrom encoder systems 70 and 71. Measurement results of waferinterferometer system 18 are used secondarily such as when correcting(calibrating) a long-term fluctuation (for example, temporal deformationof the scale) of the measurement results of encoder systems 70 and 71,or as backup at the time of output abnormality in encoder systems 70 and71. Incidentally, details on wafer interferometer system 18 will beomitted.

Alignment system ALG is an alignment system of an off-axis method placedon the +X side of projection optical system PL away by a predetermineddistance, as shown in FIG. 1. In the embodiment, as alignment systemALG, as an example, an FIA (Field Image Alignment) system is used whichis a type of an alignment sensor by an image processing method thatmeasures a mark position by illuminating a mark using a broadband (awide band wavelength range) light such as a halogen lamp and performingimage processing of the mark image. The imaging signals from alignmentsystem ALG are supplied to main controller 20 (refer to FIG. 6), via analignment signal processing system (not shown).

Incidentally, alignment system ALG is not limited to the FIA system, andan alignment sensor, which irradiates a coherent detection light to amark and detects a scattered light or a diffracted light generated fromthe mark or makes two diffracted lights (for example, diffracted lightsof the same order or diffracted lights being diffracted in the samedirection) generated from the mark interfere and detects an interferencelight, can naturally be used alone or in combination as needed. Asalignment system ALG, an alignment system having a plurality ofdetection areas like the one disclosed in, for example, U.S. PatentApplication Publication No. 2008/0088843 can be employed.

Moreover, in exposure apparatus 100 of the embodiment, a multiple pointfocal point position detection system (hereinafter shortly referred toas a multipoint AF system) AF (not shown in FIG. 1, refer to FIG. 6) bythe oblique incidence method having a similar configuration as the onedisclosed in, for example, U.S. Pat. No. 5,448,332 and the like, isarranged at the measurement station together with alignment system ALG.At least a part of a measurement operation by the multipoint AF systemAF is performed in parallel with the mark detection operation byalignment system ALG, and the positional information of the wafer tableis also measured during the measurement operation by the encoder systempreviously described. Detection signals of multipoint AF system AF aresupplied to main controller 20 (refer to FIG. 6) via an AF signalprocessing system (not shown). Main controller 20 detects positionalinformation (step information/unevenness information) of the wafer Wsurface in the Z-axis direction based on the detection signals ofmultipoint AF system AF and the measurement information of the encodersystem previously described, and in the exposure operation, performs aso-called focus leveling control of wafer W during the scanning exposurebased on prior detection results and the measurement information(positional information in the Z-axis, the θx and θy directions) of theencoder system previously described. Incidentally, multipoint AF systemcan be arranged within the exposure station in the vicinity ofprojection unit PU, and at the time of exposure operation, the so-calledfocus leveling control of wafer W can be performed by driving the wafertable while measuring the surface position information (unevennessinformation) of the wafer surface.

In exposure apparatus 100, furthermore, above reticle R, a pair ofreticle alignment detection systems 13A and 13B (not shown in FIG. 1,refer to FIG. 6) of a TTR (Through The Reticle) method which uses lightof the exposure wavelength, as is disclosed in, for example, U.S. Pat.No. 5,646,413 and the like, is arranged. Detection signals of reticlealignment systems 13A and 13B are supplied to main controller 20 via analignment signal processing system (not shown). Incidentally, reticlealignment can be performed using an aerial image measuring instrument(not shown) provided on wafer stage WST, instead of the reticlealignment system.

FIG. 6 is a block diagram showing a partially omitted control systemrelated to stage control in exposure apparatus 100. This control systemis mainly configured of main controller 20. Main controller 20 includesa so-called microcomputer (or workstation) consisting of a CPU (CentralProcessing Unit), ROM (Read Only Memory), RAM (Random Access Memory) andthe like, and has overall control over the entire apparatus.

In exposure apparatus 100 configured in the manner described above, whenmanufacturing a device, main controller 20 moves one of wafer stagesWST1 and WST2 on which the wafer is loaded within the measurementstation (measurement time movement area), and the measurement operationof the wafer by alignment system ALG and multipoint AF system isperformed. More specifically, in the measurement time movement area onthe wafer held by one of wafer stages WST1 and WST2, mark detectionusing alignment system ALG, or the so-called wafer alignment (such asEnhanced Global Alignment (EGA) disclosed in, for example, U.S. Pat. No.4,780,617 and the like) and measurement of the surface position(step/unevenness information) of the wafer using the multipoint AFsystem are performed. On such alignment, encoder system 70 (encoders 70₁ to 70 ₄) or encoder system 71 (encoders 71 ₁ to 71 ₄) obtains(measures) the positional information of wafer stages WST1 and WST2 indirections of six degrees of freedom (X, Y, Z, θx, θy, and θz).

After the measurement operation such as the wafer alignment and thelike, one of the wafer stages (WST1 or WST2) is moved to exposure timemovement area, and main controller 20 performs reticle alignment and thelike in a procedure (a procedure disclosed in, for example, U.S. Pat.No. 5,646,413 and the like) similar to a normal scanning stepper, usingreticle alignment systems 13A and 13B, fiducial mark plates (not shown)on the wafer table (WTB1 or WTB2) and the like.

Then, main controller 20 performs an exposure operation by thestep-and-scan method, based on the measurement results of the waferalignment and the like, and a pattern of reticle R is transferred ontoeach of a plurality of shot areas on wafer W. The exposure operation bythe step-and-scan method is performed by alternately repeating ascanning exposure operation where synchronous movement of reticle stageRST and wafer stage WST1 or WST2 is performed, and a movement (stepping)operation between shots where wafer stage WST1 or WST2 is moved to anacceleration starting position for exposure of the shot area. At thetime of the exposure operation, encoder system 70 (encoders 70 ₁ to 70₄) or encoder system 71 (encoders 71 ₁ to 71 ₄) obtains (measures) thepositional information of one of the wafer stages WST1 or WST2, indirections of six degrees of freedom (X, Y, Z, θx, θy, and θz).

Further, exposure apparatus 100 of the embodiment is equipped with twowafer stages WST1 and WST2. Therefore, in parallel with performing anexposure by the step-and-scan method with respect to the wafer loaded onone of the wafer stages, such as, for example, wafer stage WST1, aparallel processing operation is performed in which wafer alignment andthe like is performed on the wafer mounted on the other stage WST2.

In exposure apparatus 100 of the embodiment, as is previously described,main controller 20 obtains (measures) the positional information ofwafer stage WST1 in directions of six degrees of freedom (X, Y, Z, θx,θy, and θz) using encoder system 70 (refer to FIG. 6), within both theexposure time movement area and the measurement time movement area.Further, main controller 20 obtains (measures) the positionalinformation of wafer stage WST2 in directions of six degrees of freedom(X, Y, Z, θx, θy, and θz) using encoder system 71 (refer to FIG. 6),within both the exposure time movement area and the measurement timemovement area.

Now, the principles of position measurement in directions of threedegrees of freedom (also shortly referred to as the X-axis direction,the Y axis direction and the θz direction (X, Y, θ z)) within the XYplane by encoder systems 70 and 71 are further described. Here,measurement results or measurement values of encoder heads 60 ₁ to 60 ₄or encoders 70 ₁ to 70 ₄ refer to measurement results of encoder heads60 ₁ to 60 ₄ or encoders 70 ₁ to 70 ₄ in the measurement direction whichis not in the Z-axis direction.

In the embodiment, by employing a configuration and an arrangement ofencoder heads 60 ₁ to 60 ₄ and scale plate 21 as is previouslydescribed, at least three of the encoders head 60 ₁ to 60 ₄ constantlyface (corresponding sections 21 ₁ to 21 ₄ of) scale plate 21 within theexposure time movement area.

FIG. 7 shows a relation between a placement of encoder heads 60 ₁ to 60₄ on wafer stage WST1 and each of the sections 21 ₁ to 21 ₄ of scaleplate 21, and measurement areas A₀ to A₄ of encoder system 70.Incidentally, because the configuration of wafer stage WST2 is similarto wafer stage WST1, the description here will be made only on waferstage WST1.

When the center (coincides with the center of the wafer) of wafer stageWST1 is located in the exposure time movement area, and within a firstarea A₁ which is an area on the +X and +Y sides with respect to exposurecenter (center of exposure area IA) P (an area within a first quadrantwhose origin is exposure center P (except for area A₀)), heads 60 ₄, 60₁, and 60 ₂ on wafer stage WST1 face sections 21 ₄, 21 ₁, and 21 ₂ ofscale plate 21, respectively. In the first area A₁, effectivemeasurement values are sent to main controller 20 from these heads 60 ₄,60 ₁, and 60 ₂ (encoders 70 ₄, 70 ₁, and 70 ₂). Incidentally, theposition of wafer stages WST1 and WST2 in the description below, willrefer to the position in the center of the wafer stages (coincides withthe center of the wafer). In other words, instead of using thedescription of the position in the center of wafer stages WST1 and WST2,the description the position of wafer stages WST1 and WST2 will be used.

Similarly, when wafer stage WST1 is located in the exposure timemovement area, and also within a second area A₂, which is an area (anarea (except for area A₀) within the second quadrant whose origin isexposure center P) on the −X side and also on the +Y side with respectto exposure center P, heads 60 ₁, 60 ₂, and 60 ₃ face sections 21 ₁, 21₂, and 21 ₃ of scale plate 21, respectively. When wafer stage WST1 islocated in the exposure time movement area, and also within a third areaA₃, which is an area (an area (except for area A₀) within the thirdquadrant whose origin is exposure center P) on the −X side and also onthe −Y side with respect to exposure center P, heads 60 ₂, 60 ₃, and 60₄ face sections 21 ₂, 21 ₃, and 21 ₄ of scale plate 21, respectively.When wafer stage WST1 is located in the exposure time movement area, andalso within a fourth area A₄, which is an area (an area (except for areaA₀) within the fourth quadrant whose origin is exposure center P) on the+X side and also on the −Y side with respect to exposure center P, heads60 ₃, 60 ₄, and 60 ₁ face sections 21 ₃, 21 ₄, and 21 ₁ of scale plate21, respectively.

In the embodiment, under a condition (A≧a_(i)+2t, B≧b_(i)+2t) of theconfiguration and arrangement of encoder heads 60 ₁ to 60 ₄ and scaleplate 21 previously described, as shown in FIG. 7A, in the case waferstage WST1 is positioned within a cross-shaped area A₀ (an area whoselongitudinal direction is in the Y-axis direction and has a widthA−a_(i)−2t and an area an area whose longitudinal direction is in theX-axis direction and has a width B−b_(i)−2t that pass through exposurecenter P (hereinafter referred to as a zeroth area)) in which exposureposition P serves as the center, all of the heads 60 ₁ to 60 ₄ on waferstage WST1 face scale plate 21 (sections 21 ₁ to 21 ₄ corresponding tothe heads). Accordingly, within the zeroth area A₀, effectivemeasurement values from all of the heads 60 ₁ to 60 ₄ (encoders 70 ₁ to70 ₄) are sent to main controller 20. Incidentally, in the embodiment,in addition to the conditions (A≧a_(i)+2t, B≧b_(i)+2t) described above,condition A≧a_(i)+W+2t, B≧b_(i)+L+2t may be added taking intoconsideration the size (W, L) of the shot area on the wafer in which thepattern is formed. In this case, W and L are the width of the shot areain the X-axis direction and the Y axis direction, respectively. W and Lare equal to the distance of the scanning exposure section and thedistance of stepping in the X-axis direction, respectively.

Main controller 20 computes the position (X, Y, θ z) of wafer stage WST1in the XY plane, based on measurement results of heads 60 ₁ to 60 ₄(encoders 70 ₁ to 70 ₄). In this case, measurement values (eachdescribed as C₁ to C₄) of encoders 70 ₁ to 70 ₄ depend upon the position(X, Y, θz) of wafer stage WST1 as in formulas (1) to (4) below.C ₁=−(cos θz+sin θz)X/√2+(cos θz−sin θz)Y/√2+√2p sin θz  (1)C ₂=−(cos θz−sin θz)X/√2−(cos θz+sin θz)Y/√2+√2p sin θz  (2)C ₃=(cos θz+sin θz)X/√2−(cos θz−sin θz)Y/√2+√2p sin θz  (3)C ₄=(cos θz−sin θz)X/√2+(cos θz+sin θz)Y/√2+√2p sin θz  (4)

However, as shown in FIG. 5, p is the distance of the head in the X-axisand the Y-axis directions from the center of wafer table WTB1 (WTB2).

Main controller 20 specifies three heads (encoders) facing scale plate21 according to areas A₀ to A₄ where wafer stage WST1 is positioned andforms a simultaneous equation by choosing from the formulas (1) to (4)above the formula which the measurement values of the three headsfollow, and by solving the simultaneous equation using the measurementvalues of the three heads (encoders), computes the position (X, Y, θz)of wafer sage WST1 in the XY plane. For example, when wafer stage WST1is located in the first area A₁, main controller 20 forms a simultaneousequation from formulas (1), (2) and (4) that measurement values of heads60 ₁, 60 ₂, and 60 ₄ (encoders 70 ₁, 70 ₂, and 70 ₄) follow, and solvesthe simultaneous equation by substituting the measurement values of eachof the heads into the left side of formulas (1), (2) and (4),respectively. The position (X, Y, θz) which is calculated is expressedas X₁, Y₁, and θz₁. Similarly, in the case wafer stage WST1 is locatedin a k^(th) area A_(k), main controller 20 forms a simultaneous equationfrom formulas (k−1) (k), and (k+1) that measurement values of heads head60 _(k−1), 60 _(k), and 60 _(k+1) (encoders 70 _(k−1), 70 _(k), and 70_(k+1)) follow, and solves the simultaneous equation by substituting themeasurement values of each head into the left side of the formulas. Bysolving the equation, position (Xk, Yk, θz_(k)) is computed. Here, thenumbers from 1 to 4 which is periodically replaced is substituted intok−1, k and k+1.

Incidentally, in the case wafer stage WST1 is located in the zeroth areaA₀, main controller 20 can randomly select three heads from heads 60 ₁to 60 ₄ (encoders 70 ₁ to 70 ₄). For example, after the first waferstage WST1 has moved from the first area to the zeroth area, heads 60 ₁,60 ₂, and 60 ₄ (encoders 70 ₁, 70 ₂, and 70 ₄) corresponding to thefirst area are preferably selected.

Main controller 20 drives (position control) wafer stage WST1 within theexposure time movement area, based on the computation results (X_(k),Y_(k), θz_(k)) above.

In the case wafer stage WST1 is located within measurement time movementarea, main controller 20 measures the positional information indirections of three degrees of freedom (X, Y, θz), using encoder system70. The measurement principle and the like, here, is the same as in thecase when wafer stage WST1 is located within the measurement timemovement area, except for the point where exposure center P is replacedwith the detection center of alignment system ALG, and (sections 21 ₁ to21 ₄ of) scale plate 21 is replaced with (sections 22 ₁ to 22 ₄ of)scale plate 22.

Furthermore, main controller 20 switches and uses three heads thatincludes at least one different head, out of heads 60 ₁ to 60 ₄ thatface scale plates 21 and 22, according to the position of wafer stagesWST1 and WST2. In this case, when switching the encoder head, a linkageprocess to secure the continuity of the position measurement results ofthe wafer stage is performed, as is disclosed in, for example, U.S.Patent Application Publication No. 2008/0094592 and the like.

As previously described, scale plates 21 and 22 in exposure apparatus100 of the embodiment are configured of four sections, 21 ₁ to 21 ₄, and22 ₁ to 22 ₄, respectively. When the four sections, or to be more exact,two-dimensional diffraction grating RG formed on the lower surface ofthe four sections, are displaced with one another, a measurement erroroccurs in encoder systems 70 and 71.

FIGS. 7B and 7C typically shows a k^(th) reference coordinate systemC_(k) (k=1-4) corresponding to the position (X_(k), Y_(k), θz_(k)) ofwafer stages WST1 or WST2 computed from effective measurement values ofheads 60 _(k−1), 60 _(k), and 60 _(k+1) (encoder 70 _(k−1), 70 _(k), and70 _(k+1) or encoders 71 _(k−1), 71 _(k), and 71 _(k+1)) within thek^(th) area A_(k) (k=1-4). The four reference coordinate systems C₁ toC₄ correspond to the placement of areas A₁ to A₄ (refer to FIG. 7A) andoverlap one another in the vicinity of origin O, which serves as acenter of a cross-shaped area C₀ where adjacent reference coordinatesystems overlap one another.

When scale plate 21 is configured as designed, or in other words, in thecase two-dimensional diffraction grating RG formed on the four sections21 ₁ to 21 ₄ are not displaced with one another, origin O1 to O4 of thefour reference coordinate systems C₁ to C₄ coincide with one another(shown using reference code O in the drawing) as shown in FIG. 7B, aswell as rotation θz₁ to θz₄, and scaling Γx₁ to Γx₄ and Γy₁ to Γy₄.Accordingly, the four reference coordinate system can be combined intoone coordinate system C_(E). In other words, the position of waferstages WST1 and WST2 within exposure time movement areas A₁ to A₄ can beexpressed using position coordinate X, Y, and θz in a combinedcoordinate system C_(E).

However, when two-dimensional diffraction grating RG formed on the foursections 21 ₁ to 21 ₄ are displaced with one another, origin O₁ to O₄ ofeach of the four reference coordinate systems C₁ to C₄, rotation θz₁ toθz₄, and scaling Γx₁ to Γx₄ and Γy₁ to Γy₄ are displaced as shown inFIG. 7C, and measurement error occurs with such displacement. Therefore,the four reference coordinate systems cannot be combined to onecoordinate system C_(E) like the example shown in FIG. 7B.

Similarly, when the four sections 22 ₁ to 22 ₄ configuring scale plate22, or to be more exact, two-dimensional diffraction grating RG formedon the lower surface of the four sections 22 ₁ to 22 ₄, are displacedwith each other, a measurement error occurs in encoder system 70 or 71.

Therefore, in the embodiment, a calibration method is employed, so as tocalibrate the four reference coordinate systems C₁ to C₄ which aredisplaced with one another due to displacement between sections 21 ₁ to21 ₄, and 22 ₁ to 22 ₄ configuring scale plates 21 and 22. Now, detailsof a calibration method will be described, referring to scale plate 21as an example.

First of all, main controller 20 positions wafer stage WST1 (WST2)within area A₀, as shown in FIG. 8A. In FIG. 8A, wafer stage WST1 ispositioned in the center (right under projection optical system PL) ofarea A₀. In area A₀, all of the heads 60 ₁ to 60 ₄ installed on waferstage WST1 faces (corresponding sections 21 ₁ to 21 ₄ of) scale plate21, and sends effective measurement values to main controller 20. Maincontroller 20 obtains position (X_(k), Y_(k), θz_(k)) of wafer stageWST1, using measurement values of heads 60 _(k−1), 60 _(k), and 60_(k+2) (referred to as a k^(th) head group) which are used in the k (=1to 4)^(th) area A_(k). Main controller 20 obtains a displacement ofposition (X_(k), Y_(k)) computed from measurement values of the k (=2 to4)^(th) head group with respect to position (X₁, Y₁) computed frommeasurement values of the first head group, or in other words, obtainsan offset (O_(Xk)=X_(k)−X₁, O_(Yk)=Y_(k)−Y₁).

Incidentally, with offset (O_(Xk), O_(Yk)), an offset(O_(θzk)=θz_(k)−θz₁) of rotation θz can also be obtained at the sametime. In this case, computation of offset O_(θzk) described below is tobe omitted.

The offset (O_(Xk), O_(Yk)) obtained above is used to correct position(X_(k), Y_(k)) computed from measurement values of the k (=2 to 4)^(th)head group to (X_(k)−O_(Xk), Y_(k)−O_(Yk)). By this correction, originO_(K) of the k (=2 to 4)^(th) reference coordinate system C_(k)coincides with origin O₁ of the first reference coordinate system C₁ asshown in FIG. 8B. In the figure, the origin coinciding with each otheris indicated by reference code O.

Next, as shown in FIG. 8C, main controller 20 drives wafer stage WST1 inarea A₀ in the direction of the arrow (the X-axis direction and theY-axis direction), based on a stage position (X₁, Y₁, θz₁) computed fromthe measurement values of the first head group serving as a reference oncalibration, while setting a position by each predetermined pitch andobtaining four of position (X_(k), Y_(k) (k=1 to 4)) of wafer stageWST1, using the measurement values of the four heads groups.

Main controller 20 decides offset O_(θzk) by a least-square calculationso that square error ε_(k)=Σ((ξ_(k)−X₁)²+(ζ_(k)−Y₁)²) becomes minimal,using the four stage positions (X_(k), Y_(k) (k=1 to 4)) obtained above.However, k=2 to 4. In this case, (ξ_(k), ζ_(k)) is stage position(X_(k), Y_(k) (k=2 to 4)), to which rotational transformation has beenapplied using formula (5) below. In this case, while the least-squaresmethod is used as an example to obtain offset Oθzk, other computingmethods can also be used.

$\begin{matrix}{\begin{pmatrix}\xi_{k} \\\zeta_{k}\end{pmatrix} = {\begin{pmatrix}{\cos\mspace{11mu} O_{\theta\;{zk}}} & {{- \sin}\mspace{14mu} O_{\theta\;{zk}}} \\{\sin\mspace{11mu} O_{\theta\;{zk}}} & {\cos\mspace{14mu} O_{\theta\;{zk}}}\end{pmatrix}\begin{pmatrix}X_{k} \\Y_{k}\end{pmatrix}}} & (5)\end{matrix}$

Offset O_(θzk) obtained above is used by to correct rotation θz_(k)computed from measurement values of the k (=2 to 4)^(th) head group toθz_(k)−O_(θzk). By this correction, the direction (rotation) of thek^(th) reference coordinate system C_(k) (=2 to 4) coincides with thedirection (rotation) of the first reference coordinate system C₁, asshown in FIG. 8D.

Next, as shown in FIG. 8E, main controller 20 drives wafer stage WST1 inarea A₀ in the direction of the arrow (the X-axis direction and theY-axis direction), based on a stage position (X₁, Y₁, θz₁), whilesetting a position by each predetermined pitch and obtaining four ofposition (X_(k), Y_(k) (k=1 to 4)) of wafer stage WST1, as in theearlier case.

Main controller 20 decides scaling (Γ_(Xk), Γ_(Yk)) by a least-squarecalculation so that square error εk=Σ((ξ_(k)′−X₁)²+(ζ_(k)′−Y₁)²) becomesminimal, using the four stage positions (X_(k), Y_(k) (k=1-4)) obtainedabove. However, k=2 to 4. In this case, (ξ_(k)′, ζ_(k)′) is stageposition (X_(k), Y_(k) (k=2-4)), to which scale transformation has beenapplied using formula (6) below.

$\begin{matrix}{\begin{pmatrix}\xi_{k}^{\prime} \\\zeta_{k}^{\prime}\end{pmatrix} = {\begin{pmatrix}{1 + \Gamma_{Xk}} & 0 \\0 & {1 + \Gamma_{Yk}}\end{pmatrix}\begin{pmatrix}X_{k} \\Y_{k}\end{pmatrix}}} & (6)\end{matrix}$

Scaling (Γ_(Xk), Γ_(Yk)) obtained above is used to correct position(X_(k), Y_(k)) computed from measurement values of the k (=2 to 4)^(th)head group to (X_(k)/(1+Γ_(Xk)), Y_(k)/(1+Γ_(Yk))). By this correction,the scaling of the k^(th) reference coordinate system C_(k) (=2 to 4)coincides with the scaling of the first reference coordinate system C₁as shown in FIG. 8F.

The four reference coordinate systems C₁ to C₄ whose position, rotation,and scaling have been calibrated by the processing described above arecombined into one coordinate system (a combined coordinate system) C_(E)which covers exposure time movement area A₀ to A₄.

Incidentally, instead of the processing described so far, the offset andscaling (O_(Xk), O_(Yk), O_(θzk), Γ_(Xk), Γ_(Yk) (k=2-4)) can also beobtained by the following processing. In other words, as shown in FIGS.8C and 8E, main controller 20 drives wafer stage WST1 in area A₀ in thedirection of the arrow (the X-axis direction and the Y-axis direction),based on a stage position (X₁, Y₁, θz₁), while setting a position byeach predetermined pitch and obtaining four of position (X_(k), Y_(k)(k=1-4)) of wafer stage WST1. An offset and scaling (O_(Xk), O_(Yk),O_(θzk), Γ_(Xk), Γ_(Yk)) are determined by least square operation sothat main controller 20 uses four ways of bought stage location (X_(k),Y_(k) (k=1-4)), and square error ε_(k)=Σ((ξ″_(k)−X₁)²+(ζ″_(k)−Y₁)²) isminimized. However, k=2 to 4. In this case, (ξ″_(k), ζ″_(k)) is stageposition (X_(k), Y_(k) (k=2-4)) to which transformation has been appliedusing formula (7) below.

$\begin{matrix}{\begin{pmatrix}\xi_{k}^{''} \\\zeta_{k}^{''}\end{pmatrix} = {{\begin{pmatrix}{1 + \Gamma_{Xk}} & 0 \\0 & {1 + \Gamma_{Yk}}\end{pmatrix}\begin{pmatrix}{\cos\mspace{14mu} O_{\theta\;{zk}}} & {{- \sin}\mspace{11mu} O_{\theta\;{zk}}} \\{\sin\mspace{14mu} O_{\theta\;{zk}}} & {\cos\mspace{14mu} O_{\theta\;{zk}}}\end{pmatrix}\begin{pmatrix}X_{k} \\Y_{k}\end{pmatrix}} + \begin{pmatrix}O_{Xk} \\O_{Yk}\end{pmatrix}}} & (7)\end{matrix}$

Further, in the processing above, while the offset and scaling of thesecond to fourth reference coordinate systems C₂ to C₄ were obtaineddirectly with the first reference coordinate system C₁, the offset andscaling can also be obtained indirectly. For example, the offset andscaling (O_(X2), O_(Y2), O_(θz2), Γ_(X2), Γ_(Y2)) is obtained for thesecond reference coordinate system C₂ which uses the first referencecoordinate system C₁ as a reference according to the procedure describedabove. Similarly, the offset and scaling (O_(X32), O_(Y32), O_(θz32),Γ_(X32), Γ_(Y32)) is obtained for the third reference coordinate systemC₃ which uses the second reference coordinate system C₂ as a reference.From these results, an offset and scaling for the third referencecoordinate system C₃ using the first reference coordinate system C₁ as areference can be obtained (O_(X3)=O_(X32)+O_(X2), O_(Y3)=O_(Y32)+O_(Y2),O_(θz3)=O_(θz32)+O_(θz2), Γ_(X3)=Γ_(X32)·Γ_(X2), Γ_(Y3)=Γ_(Y32)·Γ_(Y2)).Similarly, the offset and scaling of the fourth reference coordinate C₄using the third reference coordinate system C₃ can be obtained, and theoffset and scaling of the fourth reference coordinate C₄ using the firstreference coordinate system C₁ as a reference can also be obtained usingthe results.

Main controller 20 also calibrates the four reference coordinates withrespect to scale plate 22 according to a similar procedure, and combinesthe four reference coordinate systems into one coordinate system (acombined coordinate system) C_(A) (refer to FIG. 7B) which coversalignment time movement area.

Finally, main controller 20 obtains the displacement of the position,rotation, and scaling between combined coordinate system C_(E) whichcovers the exposure time movement areas A₀ to A₄ and combined coordinatesystem C_(A) which covers the alignment time movement area. As shown inFIG. 9A, main controller 20 obtains (measures) the positionalinformation of wafer stage WST1 using encoder system 70, and driveswafer stage WST1 based on the results and positions the first fiducialmark plate FM1 on wafer table WTB1 directly under (exposure center P of)projection optical system PL. Main controller 20 detects two (a pair of)reference marks formed on first fiducial mark plate FM1, using a pair ofreticle alignment systems 13A and 13B. Then, main controller 20 driveswafer stage WST1 based on measurement results of encoder system 70, andpositions the second fiducial mark plate FM2 on wafer table WTB1directly under (exposure center P of) projection optical system PL, anddetects a reference mark formed on second fiducial mark plate FM2 usingone of the pair of reticle alignment systems 13A and 13B. Maincontroller 20 obtains the position of the origin, rotation, and scalingof combined coordinate system C_(E) from the detection results (in otherwords, the two-dimensional position coordinates of the three referencemarks) of the three reference marks.

Main controller 20 moves wafer stage WST1 to the measurement timemovement area. Here, main controller 20 measures the positionalinformation of wafer stage WST1, using wafer interferometer system 18 inthe area between exposure time movement area A₀ to A₄ and themeasurement time movement area and encoder system 70 in the measurementtime movement area, and drives (controls the position of) wafer stageWST1 based on the results. After the movement, as shown in FIGS. 10A and10B, main controller 20 detects the three reference marks as ispreviously described using alignment system ALG, and obtains theposition of the origin, rotation and scaling of combined coordinatesystem C_(A) from the detection results. Incidentally, while it isdesirable for the three reference marks subject to detection of reticlealignment system 13A to be the same marks as the three reference markssubject to detection of alignment system ALG, when the same referencemarks cannot be detected in reticle alignment systems 13A and 13B andalignment system ALG, different reference marks can be subject todetection in reticle alignment systems 13A and 13B and alignment systemALG since the positional relation between the reference marks is known.

Incidentally, also in the case when the wafer stage is moved between theexposure time movement area and the measurement time movement area,position control of the wafer stage can be performed using then encodersystem. Further, a linkage process (a phase linkage and/or a coordinatelinkage) is performed in each of the exposure time movement area and themeasurement time movement area. Coordinate linkage, in this case, refersto a linkage process of setting a measurement value with respect to anencoder which will be used after the switching so that the positioncoordinate of wafer stage WST which is computed coincides completelybefore and after the switching of the encoder (head), and to re-set thephase offset on this setting. While the phase linkage method isbasically similar to a coordinate linkage method, usage of the phaseoffset is different, and the phase linkage method refers to a linkagemethod in which the phase offset which is already set is continuouslyused without resetting the phase offset, and only the counter value isre-set.

Main controller 20 obtains the displacement of the origin, rotation, andscaling between combined coordinate systems C_(E) and C_(A) from theposition of origin, rotation, and scaling of combined coordinate systemC_(E) and the position of origin, rotation, and scaling of combinedcoordinate system C_(A). Main controller 20 can use this displacement,for example, to convert results of wafer alignment measured on combinedcoordinate system C_(A), such as for example, to convert arraycoordinates (or a position coordinate of an alignment mark on the wafer)of a plurality of shot area on the wafer to an array coordinate of aplurality of shot areas on the wafer on combined coordinate systemC_(E), and drives (controls the position of) wafer stage WST1 oncombined coordinate system C_(E) at the time of wafer exposure, based onthe array coordinates which have been converted.

Main controller 20 performs the calibration method described above eachtime exposure processing of a wafer (or each time exposure processing ofa predetermined number of wafers) is performed. In other words, prior towafer alignment using alignment system ALG, encoder systems 70 and 71are calibrated on the usage of scale plate 22 as previously described(the four reference coordinate systems C₁ to C₄ are combined intocombined coordinate system C_(A)). Measurement operations such as waferalignment to the wafer subject to exposure are performed, using encodersystems 70 and 71 which have been calibrated (on combined coordinatesystem C_(A)). Successively, prior to the exposure processing of thewafer, encoder systems 70 and 71 are calibrated on the usage of scaleplate 22 as previously described (the four reference coordinate systemsC₁ to C₄ are combined into combined coordinate system C_(E)). Further,displacement (relative position, relative rotation, and relativescaling) of the position, rotation, and scaling between combinedcoordinate systems C_(A) and C_(E) is obtained. Results (for example,array coordinates of a plurality of shot areas on the wafer) of waferalignment measured on combined coordinate system C_(A) using theseresults are converted into array coordinates of a plurality of shotareas on the wafer on combined coordinate system C_(E), and exposureprocessing on the wafer is performed by driving (controlling theposition of) wafer stages WST1 and WST2 holding the wafer on combinedcoordinate system C_(E), based on the array coordinates after theconversion.

Incidentally, as the calibration process (calibration method), while themeasurement values of the encoder system can be corrected, otherprocessing can also be employed. For example, other methods can also beapplied, such as driving (performing position control of) the waferstage while adding an offset to the current position or the targetposition of the wafer stage with the measurement errors serving as anoffset, or correcting the reticle position only by the measurementerror.

Next, the principle of position measurement in directions of threedegrees of freedom (Z, θx, θy) by encoder systems 70 and 71 will befurther described. Here, measurement results or measurement values ofencoder heads 60 ₁ to 60 ₄ or encoders 701 to 704 refer to measurementresults of encoder heads 60 ₁ to 60 ₄ or encoders 701 to 704 in theZ-axis direction.

In the embodiment, by employing a configuration and an arrangement ofencoder heads 60 ₁ to 60 ₄ and scale plate 21 as is previouslydescribed, at least three of the encoders head 60 ₁ to 60 ₄ face(corresponding sections 21 ₁ to 21 ₄ of) scale plate 21 according toarea A₀ to A₄ where wafer stage WST1 (or WST2) is located within theexposure time movement area. Effective measurement values are sent tomain controller 20 from the heads (encoders) facing scale plate 21.

Main controller 20 computes the position (Z, θx, θy) of wafer table WTB1(or WTB2), based on measurement results of encoders 70 ₁ to 70 ₄ (or 71₁ to 71 ₄). Here, the measurement values (each expressed as D₁ to D₄,respectively, to distinguish the values from measurement values C₁ to C₄in a measurement direction which is not in the Z-axis direction as ispreviously described, namely, in a uniaxial direction in the XY plane)of encoders 70 ₁ to 70 ₄ (or 71 ₁ to 71 ₄) in the Z-axis directiondepend upon the position (Z, θx, θy) of wafer stage WST1 (or WST2) as informulas (8) to (11) below.D ₁ =−p tan θy+p tan θx+Z  (8)D ₂ =p tan θy+p tan θx+Z  (9)D ₃ =p tan θy−p tan θx+Z  (10)D ₄ =−p tan θy−p tan θx+Z  (11)

However, p is the distance (refer to FIG. 5) of the head in the X-axisand the Y-axis directions from the center of wafer table WTB1 (WTB2).

Main controller 20 selects the formulas that the measurement values ofthe three heads (encoders) follow according to areas A₀ to A₄ wherewafer stage WST1 (WST2) is positioned from formula (8) to (11) describedabove, and by substituting and solving the measurement values of thethree heads (encoders) into the simultaneous equation built from thethree formulas which were selected, the position (Z, θx, θy) of wafertable WTB1 (WTB2) is computed. For example, when wafer stage WST1 (WST2)is located in the first area A₁, main controller 20 forms a simultaneousequation from formulas (8), (9) and (11) that measurement values ofheads 60 ₁, 60 ₂, and 60 ₄ (encoders 70 ₁, 70 ₂, and 70 ₄) follow, andsolves the simultaneous equation by substituting the measurement valuesinto the left side of formulas (8), (9) and (11), respectively. Theposition (Z, θx, θy) which is calculated is expressed as Z₁, θx₁, andθy₁. Similarly, in the case wafer stage WST1 is located in a k^(th) areaA_(k), main controller 20 forms a simultaneous equation from formulas((k−1)+7), (k+7), and ((k+1)+7) that measurement values of heads head 60_(k−1), 60 _(k), and 60 _(k+1) (encoders 70 _(k−1), 70 _(k), and 70_(k+1)) follow, and solves the simultaneous equation by substituting themeasurement values of each head into the left side of formulas ((k−1)+7)(k+7) and ((k+1)+7). By solving the equation, position (Z_(k), θx_(k),θy_(k)) is computed. Here, the numbers from 1 to 4 which is periodicallyreplaced is substituted into k−1, k and k+1.

Incidentally, in the case wafer stage WST1 (or WST2) is located in the0^(th) area A₀, three heads from heads 60 ₁ to 60 ₄ (encoders 70 ₁ to 70₄ or 71 ₁ to 71 ₄) can be randomly selected, and a simultaneous equationmade from the formulas that the measurement values of the selected threeheads follow can be used.

Based on the computation results (Z_(k), θx_(k), θy_(k)) and stepinformation (focus mapping data) previously described, main controller20 performs a focus leveling control on wafer table WTB1 (WTB2) withinthe exposure time movement area.

In the case wafer stage WST1 (or WST2) is located within measurementtime movement area, main controller 20 measures the positionalinformation in directions of three degrees of freedom (Z, θx, θy) ofwafer table WTB1 (WTB2) using encoder system 70 or 71. The measurementprinciple and the like, here, is the same as in the case when waferstage WST1 is located within the exposure time movement area previouslydescribed, except for the point where the exposure center is replacedwith the detection center of alignment system ALG, and (sections 21 ₁ to21 ₄ of) scale plate 21 is replaced with (sections 22 ₁ to 22 ₄ of)scale plate 22. Based on the measurement results of encoder system 70 or71, main controller 20 performs a focus leveling control on wafer tableWTB1 (WTB2). Incidentally, in the measurement time movement area(measurement station), focus leveling does not necessarily have to beperformed. In other words, a mark position and the step information(focus mapping data) should be obtained in advance, and by deducting theZ tilt of the wafer stage at the time of obtaining the step informationfrom the step information, the step information of the reference surfaceof the wafer stage, such as the step information with the upper surfaceserving as the reference surface, should be obtained. And, at the timeof exposure, focus leveling becomes possible based on the positionalinformation in directions of three degrees of freedom (Z, θx, θy) ofthis step information and (the reference surface of) the wafer surface.

Furthermore, main controller 20 switches and uses three heads thatinclude at least one different head out of heads 60 ₁ to 60 ₄ that facescale plates 21 and 22, according to the position of wafer stages WST1and WST2. In this case, when an encoder head is switched, the linkageprocess is performed to secure the continuity of the measurement resultsof the position of wafer table WTB1 (or WTB2).

As previously described, scale plates 21 and 22 in exposure apparatus100 of the embodiment are configured of four sections, 21 ₁ to 21 ₄, and22 ₁ to 22 ₄, respectively. When the height and tilt of the foursections are displaced with one another, a measurement error occurs inencoder systems 70 and 71. Therefore, the calibration method as ispreviously described is employed so as to calibrate the four referencecoordinate system C₁ to C₄ which are displaced with one another due todisplacement of height and tilt between sections 21 ₁ to 21 ₄, and 22 ₁to 22 ₄.

Now, an example of a calibration method will be described, with a caseusing encoder system 70 as an example.

Main controller 20, as shown in FIGS. 8C and 8E, drives wafer stage WST1in area A₀ in the direction of the arrow (the X-axis direction and theY-axis direction), based on measurement results (X₁, Y₁, θz₁) of theposition of wafer stage WST1 measured by encoder system 70, whilesetting a position by each predetermined pitch and obtaining four ofposition (Z_(k), θx_(k), θy_(k) (k=1-4)) of wafer table WTB1, using themeasurement values of the four heads groups. Using these results, maincontroller 20 obtains the displacement of position (Z_(k), θx_(k),θy_(k)) computed from the measurement values of the k (=2-4)^(th) headgroup with respect to position (Z₁, θx₁, θy₁) computed from themeasurement values of the first head group, or in other words, obtainsan offset (O_(Zk)=Z_(k)−Z₁, O_(θxk)=θx_(k)−θx₁, O_(θyk)=θy_(k)−θy₁).Furthermore, main controller 20 averages offset (O_(Zk), O_(θxk),O_(θyk)) which is obtained for each positioning.

The offset (O_(Zk), O_(θxk), O_(θyk)) obtained above is used to correctposition ((Z_(k), θx_(k), θy_(k)) computed from measurement values ofthe k (=2-4)th head group to Z_(k)−O_(Zk), θx_(k)−O_(θxk), andθy_(k)−O_(θyk), respectively. By this correction, height Z and tilt θxand θy of the k^(th) reference coordinate system Ck (k=2-4) coincideswith height Z and tilt θx and θy of the reference coordinate system C₁.In other words, the four reference coordinate systems C₁ to C₄ arecombined into one coordinate system (a combined coordinate system) C_(E)which covers exposure time movement area A₀ to A₄.

Main controller 20 also calibrates the four reference coordinates withrespect to encoder system 71 according to a similar procedure, andcombines the four reference coordinate systems into one coordinatesystem (a combined coordinate system) C_(A) which covers alignment timemovement area.

Main controller 20 performs the calibration method described above aspreviously described, each time exposure processing is performed on thewafer (or each time exposure processing is performed on a predeterminednumber of wafers). In other words, prior to wafer alignment usingalignment system ALG, encoder system 70 or (71) on the usage of scaleplate 22 is calibrated as previously described (the four referencecoordinate systems C₁ to C₄ are combined into combined coordinate systemC_(A)). And, main controller 20 performs wafer alignment on the wafersubject to exposure, using encoder system 70 or (71) which has beencalibrated (on combined coordinate system C_(A)). Successively, prior tothe exposure processing of a wafer, encoder system 70 (or 71) on theusage of scale plate 22 is calibrated as previously described (the fourreference coordinate systems C₁ to C₄ are combined into combinedcoordinate system C_(E)). Then, main controller 20 obtains (measures)the positional information of wafer table WTB1 (or WTB2) holding a waferusing encoder system 70 (or 71) (on combined coordinate system C_(E))which has been calibrated, and based on the measurement results andresults of wafer alignment, drives (controls the position of) wafertable WTB1 (or WTB2) when exposing the wafer.

As described in detail above, according to exposure apparatus 100 of theembodiment, within area A₀ where of four heads 60 ₁ to 60 ₄ installed onwafer stages WST1 and WST2, heads included in the first head group andthe second head group to which three heads each belong that include onehead different from each other face the corresponding areas (sections 21₁ to 21 ₄ and 22 ₁ to 22 ₄) on scale plates 21 and 22, main controller20 drives (controls the position of) wafer stages WST1 and WST2 based onpositional information which is obtained using the first head group, aswell as obtain the displacement (displacement of position, rotation, andscaling) between the first and second reference coordinate systems C₁and C₂ corresponding to the first and second head groups using thepositional information obtained using the first and second head groups.And by main controller 20 using the results and correcting measurementresults obtained using the second head group, the displacement betweenthe first and second reference coordinate systems C₁ and C₂ iscalibrated, which makes it possible to correct the measurement errorsthat come with the displacement between areas on scale plates 21 and 22where each of the four heads 60 ₁ to 60 ₄ face.

Further, according to exposure apparatus 100 of the embodiment, becauseencoder systems 70 and 71 are calibrated using the calibration methoddescribed above and displacement of between the four referencecoordinate systems C₁ to C₄ is corrected, it becomes possible to measurethe positional information of wafer stages WST1 and WST2 using encodersystems 70 and 71 and to drive (control the position of) wafer stagesWST1 and WST2 with high precision.

Further, according to exposure apparatus 100 of the embodiment, by maincontroller 20 detecting the three reference marks provided on waferstages WST1 and WST2 using reticle alignment systems 13A and 13B andalignment system ALG, relative position, relative rotation, and relativescaling of combined coordinate systems C_(E) and C_(A) corresponding toexposure time movement area and measurement time movement area,respectively, are obtained. Then, main controller 20 uses the results,which allows results of wafer alignment measured on combined coordinatesystem C_(A), such as for example, array coordinates of a plurality ofshot areas on the wafer are converted into array coordinates of aplurality of shot areas on the wafer on combined coordinate system CE,and the wafer can be exposed by driving (controlling the position of)wafer stages WST1 and WST2 on combined coordinate system C_(E) using theresults.

Incidentally, in the embodiment above, when wafer stage WST1 locatedwithin the zeroth area A₀, all the heads 60 ₁ to 60 ₄ on wafer stageWST1 face scale plate 21 (corresponding sections 21 ₁ to 21 ₄).Accordingly, within the zeroth area A₀, effective measurement valuesfrom all of the heads 60 ₁ to 60 ₄ (encoders 70 ₁ to 70 ₄) are sent tomain controller 20. Accordingly, main controller 20 can drive (controlthe position of) wafer stages WST1 and WST2 within area A₀ where of fourheads 60 ₁ to 60 ₄, heads included in a k^(th) head group (k=1 to 4)previously described to which three heads belong that include one headdifferent from each other face the corresponding area (sections 21 ₁ to21 ₄) on scale plate 21, based on positional information which isobtained using at least one head in the k^(th) head group, such as forexample, at least one of the first positional information which isobtained using the first head group and the second positionalinformation which is obtained using the second head group. In such acase, even if the coordinate system (section of scale plate 21)corresponding to the first head group and the second head group isdifferent, wafer stages WST1 and WST2 can be driven with high precisionwithout being affected by this. The same is true also in the case ofusing scale plate 22.

Incidentally, in the embodiment described above, in the calibrationprocess of a displacement of the four reference coordinate systems C₁ toC₄ which occurs due to a displacement of sections 21 ₁ to 21 ₄ and 22 ₁to 22 ₄ configuring scale plates 21 and 22, not all of position,rotation, and scaling require attention, and one or any two factors maybe noted, or other factors (such as the orthogonal degree) may be addedor substituted.

Further, at least one auxiliary head can be provided in the vicinity ofeach of the heads on the four corners of the upper surface of the wafertable, and in the case a measurement abnormality occurs in the mainheads, the measurement can be continued by switching to the auxiliaryhead nearby. In such a case, the placement condition previouslydescribed may also be applied to the auxiliary head.

Incidentally, in the embodiment above, while the case wheretwo-dimensional diffraction grating RG was formed on the lower surfaceof sections 21 ₁ to 21 ₄ of scale plate 21 and sections 22 ₁ to 22 ₄ ofscale plate 22 was described as an example, besides this, the embodimentdescribed above can also be applied in the case when a one-dimensionaldiffraction grating whose periodic direction is only in the measurementdirection (in a uniaxial direction within the XY plane) of thecorresponding encoder heads 60 ₁ to 60 ₄ is formed.

Incidentally, in the embodiment above, while the case has been describedwhere drive (position control) of wafer stages WST1 and WST2 isperformed within area A₀ where of the four heads 60 ₁ to 60 ₄ mounted onwafer stages WST1 and WST2, heads included in a first head group and asecond head group to which three heads including one head different fromeach other belong face the corresponding area on scale plates 21 and 22,based on the positional information which is obtained using the firsthead group, and measurement errors which accompany the displacementoccurring in the area above scale plates 21 and 22 where each of thefour heads 60 ₁ to 60 ₄ faces are corrected, by obtaining thedisplacement (displacement of position, rotation, and scaling) betweenthe first and second reference coordinate systems C₁ and C₂corresponding to the first and second head groups using the positionalinformation obtained using the first and second head groups, and byusing the results, correcting the measurement results which can beobtained using the second head group, besides this, for example, thecorrection information of the positional information of the stage can beobtained by the encoder system, by moving the wafer stage within an areawhere the position can be measured for each of the plurality (a secondnumber) of heads which is more than the plurality (a first number) ofheads used for controlling the position of the wafer stage, or in otherwords, for example, the stage can move within a cross-shaped area A0described in the embodiment above, and can obtain the correctioninformation by using a redundancy head.

In this case, while this correction information is used by maincontroller 20 to correct the encoder measurement value itself, thecorrection information can be used by other processing. For example,other methods can also be applied, such as driving (performing positioncontrol of) the wafer stage while adding an offset to the currentposition or the target position of the wafer stage with the measurementerrors serving as an offset, or correcting the reticle position only bythe measurement error.

Further, in the embodiment above, while the case has been describedwhere the displacement (displacement of position, rotation, and scaling)between the first and the second reference coordinate systems C₁ and C₂corresponding to the first and second head groups was obtained using thepositional information which was obtained using the first and the secondhead groups, besides this, for example, the exposure apparatus can beequipped with a position measurement system (for example, an encodersystem) which obtains the positional information of the wafer stagebased on an output of heads which irradiates a measurement beam on ameasurement plane which is configured of a plurality of scale plates andis placed roughly parallel to the XY plane outside of the wafer stage inthe vicinity of the exposure position of the wafer, of the plurality ofheads provided on the wafer stage and a control system which drives thewafer stage based on the positional information obtained by themeasurement system, and switches the heads used by the positionmeasurement system to obtain the positional information from theplurality of heads according to the position of the wafer stage, and thecontrol system can obtain the positional relation between the pluralityscale plates corresponding to the plurality of heads within a first areawithin the first area of the movable body where the plurality of headsface the measurement plane. In this case, of the plurality of heads, theplurality of head groups to which a plurality of heads including atleast one head different from each other can face the plurality of scaleplates, respectively.

In this case, the positional relation between the plurality of scaleplates can be used not only to correct the encoder measurement values,but also in other processing as well. For example, other methods canalso be applied, such as driving (performing position control of) thewafer stage while adding an offset to the current position or the targetposition of the wafer stage with the measurement errors serving as anoffset, or correcting the reticle position only by the measurementerror.

Further, in the embodiment above, as each of the heads 60 ₁ to 60 ₄(encoders 70 ₁ to 70 ₄), while the case has been described where atwo-dimensional encoder whose measurement direction is in a uniaxialdirection within the XY plane and in the Z-axis direction was employedas an example, besides this, a one-dimensional encoder whose measurementdirection is in a uniaxial direction within the XY plane and aone-dimensional encoder (or a surface position sensor and the like of anon-encoder method) whose measurement direction is in the Z-axisdirection can also be employed. Or, a two-dimensional encoder whosemeasurement direction is in two axial directions which are orthogonal toeach other in the XY plane can be employed. Or, a two-dimensionalencoder whose measurement direction is in two axial directions which areorthogonal to each other in the XY plane can be employed. Furthermore, athree-dimensional encoder (3 DOF sensor) whose measurement direction isin the X-axis, the Y-axis, and the Z-axis direction can also beemployed.

Incidentally, in each of the embodiments described above, while the casehas been described where the exposure apparatus is a scanning stepper,the present invention is not limited to this, and the embodimentdescribed above can also be applied to a static exposure apparatus suchas a stepper. Even in the case of a stepper, by measuring the positionof a stage (table) on which the object subject to exposure is mountedusing an encoder, position measurement error caused by air fluctuationcan substantially be nulled, which is different from when measuring theposition of this stage (table) by an interferometer, and it becomespossible to position the stage (table) with high precision based on themeasurement values of the encoder, which in turn makes it possible totransfer a reticle pattern on the wafer with high precision. Further,the embodiment described above can also be applied to a projectionexposure apparatus by a step-and-stitch method that synthesizes a shotarea and a shot area. Moreover, the embodiment described above can alsobe applied to a multi-stage type exposure apparatus equipped with aplurality of wafer stages, as is disclosed in, for example, U.S. Pat.No. 6,590,634, U.S. Pat. No. 5,969,441, U.S. Pat. No. 6,208,407 and thelike. Further, the embodiment described above can also be applied to anexposure apparatus which is equipped with a measurement stage includinga measurement member (for example, a reference mark, and/or a sensor andthe like) separate from the wafer stage, as disclosed in, for example,U.S. Patent Application Publication No. 2007/0211235, and U.S. PatentApplication Publication No. 2007/0127006 and the like.

Further, the exposure apparatus in the embodiment above can be of aliquid immersion type, like the ones disclosed in, for example, PCTInternational Publication No. 99/49504, U.S. Patent ApplicationPublication No. 2005/0259234 and the like.

Further, the magnification of the projection optical system in theexposure apparatus of the embodiment above is not only a reductionsystem, but also may be either an equal magnifying system or amagnifying system, and projection optical system PL is not only adioptric system, but also may be either a catoptric system or acatadioptric system, and in addition, the projected image may be eitheran inverted image or an upright image.

In addition, the illumination light IL is not limited to ArF excimerlaser light (with a wavelength of 193 nm), but may be ultraviolet light,such as KrF excimer laser light (with a wavelength of 248 nm), or vacuumultraviolet light, such as F₂ laser light (with a wavelength of 157 nm).As disclosed in, for example, U.S. Pat. No. 7,023,610, a harmonic wave,which is obtained by amplifying a single-wavelength laser beam in theinfrared or visible range emitted by a DFB semiconductor laser or fiberlaser as vacuum ultraviolet light, with a fiber amplifier doped with,for example, erbium (or both erbium and ytterbium), and by convertingthe wavelength into ultraviolet light using a nonlinear optical crystal,can also be used.

Further, in the embodiment above, a transmissive type mask (reticle) isused, which is a transmissive substrate on which a predetermined lightshielding pattern (or a phase pattern or a light attenuation pattern) isformed. Instead of this reticle, however, as is disclosed in, forexample, U.S. Pat. No. 6,778,257 description, an electron mask (which isalso called a variable shaped mask, an active mask or an imagegenerator, and includes, for example, a DMD (Digital Micromirror Device)that is a type of a non-emission type image display device (spatiallight modulator) or the like) on which a light-transmitting pattern, areflection pattern, or an emission pattern is formed according toelectronic data of the pattern that is to be exposed can also be used.In the case of using such a variable shaped mask, because the stagewhere a wafer, a glass plate or the like is mounted is scanned withrespect to the variable shaped mask, an equivalent effect as theembodiment above can be obtained by measuring the position of the stageusing an encoder.

Further, as is disclosed in, for example, PCT International PublicationNo. 2001/035168, the embodiment above can also be applied to an exposureapparatus (lithography system) that forms line-and-space patterns on awafer W by forming interference fringes on wafer W.

Moreover, as disclosed in, for example, U.S. Pat. No. 6,611,316, theembodiment above can also be applied to an exposure apparatus thatsynthesizes two reticle patterns via a projection optical system andalmost simultaneously performs double exposure of one shot area by onescanning exposure.

Incidentally, an object on which a pattern is to be formed (an objectsubject to exposure to which an energy beam is irradiated) in theembodiment above is not limited to a wafer, but may be other objectssuch as a glass plate, a ceramic substrate, a film member, or a maskblank.

The application of the exposure apparatus is not limited to an exposureapparatus for fabricating semiconductor devices, but can be widelyadapted to, for example, an exposure apparatus for fabricating liquidcrystal devices, wherein a liquid crystal display device pattern istransferred to a rectangular glass plate, as well as to exposureapparatuses for fabricating organic electroluminescent displays, thinfilm magnetic heads, image capturing devices (e.g., CCDs),micromachines, and DNA chips. Further, the embodiment described abovecan be applied not only to an exposure apparatus for producingmicrodevices such as semiconductor devices, but can also be applied toan exposure apparatus that transfers a circuit pattern onto a glassplate or silicon wafer to produce a mask or reticle used in a lightexposure apparatus, an EUV exposure apparatus, an X-ray exposureapparatus, an electron-beam exposure apparatus, and the like.

Incidentally, the disclosures of all publications, the Published PCTInternational Publications, the U.S. patent applications and the U.S.patents that are cited in the description so far related to exposureapparatuses and the like are each incorporated herein by reference.

Electronic devices such as semiconductor devices are manufacturedthrough the steps of; a step where the function/performance design ofthe device is performed, a step where a reticle based on the design stepis manufactured, a step where a wafer is manufactured from siliconmaterials, a lithography step where the pattern formed on a mask istransferred onto an object such as the wafer by the exposure apparatusin the embodiment above, a development step where the wafer that hasbeen exposed is developed, an etching step where an exposed member of anarea other than the area where the resist remains is removed by etching,a resist removing step where the resist that is no longer necessary whenetching has been completed is removed, a device assembly step (includinga dicing process, a bonding process, the package process), inspectionsteps and the like. In this case, because the exposure apparatus and theexposure method in the embodiment above are used in the lithographystep, devices having high integration can be produced with good yield.

Further, the exposure apparatus (the pattern forming apparatus) of theembodiment above is manufactured by assembling various subsystems, whichinclude the respective constituents that are recited in the claims ofthe present application, so as to keep predetermined mechanicalaccuracy, electrical accuracy and optical accuracy. In order to securethese various kinds of accuracy, before and after the assembly,adjustment to achieve the optical accuracy for various optical systems,adjustment to achieve the mechanical accuracy for various mechanicalsystems, and adjustment to achieve the electrical accuracy for variouselectric systems are performed. A process of assembling varioussubsystems into the exposure apparatus includes mechanical connection,wiring connection of electric circuits, piping connection of pressurecircuits, and the like among various types of subsystems. Needless tosay, an assembly process of individual subsystem is performed before theprocess of assembling the various subsystems into the exposureapparatus. When the process of assembling the various subsystems intothe exposure apparatus is completed, a total adjustment is performed andvarious kinds of accuracy as the entire exposure apparatus are secured.Incidentally, the making of the exposure apparatus is preferablyperformed in a clean room where the temperature, the degree ofcleanliness and the like are controlled.

While the above-described embodiment of the present invention is thepresently preferred embodiment thereof, those skilled in the art oflithography systems will readily recognize that numerous additions,modifications, and substitutions may be made to the above-describedembodiment without departing from the spirit and scope thereof. It isintended that all such modifications, additions, and substitutions fallwithin the scope of the present invention, which is best defined by theclaims appended below.

What is claimed is:
 1. An exposure apparatus which exposes an objectwith an illumination light via a projection optical system, theapparatus comprising: a stage having a holder configured to hold theobject; a driving system having an electromagnetic motor, which drivesthe stage by the electromagnetic motor, a part of the electromagneticmotor being provided at the stage; an encoder system having a pluralityof heads provided at the stage, which measures positional information ofthe stage by irradiating a measurement beam from below via each of theplurality of heads onto a measurement plane arranged substantiallyparallel to a predetermined plane perpendicular to an optical axis ofthe projection optical system; and a controller coupled with the drivingsystem and the encoder system, which controls a drive of the stage basedon the measured positional information, wherein the measurement plane isdefined by a plurality of scale plates which are arranged around anexposure position where exposure of the object is performed via theprojection optical system and on each of which a reflective grating isformed, in a part including the exposure position, of a first movementarea where the stage is moved in an exposure operation of the object,the encoder system is capable of measuring the positional information ofthe stage by the plurality of heads that respectively face the pluralityof scale plates, and in another part of the first movement area, theencoder system is capable of measuring the positional information of thestage by remaining heads after excluding one head of the plurality ofheads, and the controller decides calibration information of the encodersystem based on the positional information of the stage measured by theencoder system in the part including the exposure position of the firstmovement area.
 2. The exposure apparatus according to claim 1, whereinin the part including the exposure position of the first movement area,the positional information of the stage can be measured by four heads ofthe encoder system, and in the another part of the first movement area,the positional information of the stage can be measured by three headsof the four heads.
 3. The exposure apparatus according to claim 2,wherein in the another part of the first movement area, a combination ofthree heads used in the measurement, of the four heads, differsdepending on a position of the stage.
 4. The exposure apparatusaccording to claim 1, wherein in the part including the exposureposition of the first movement area, the positional information measuredby three heads of four heads of the encoder system is used in drivecontrol of the stage, and in the another part of the first movementarea, the positional information measured by three heads, of the fourheads, having one head different from the three heads used in the partincluding the exposure position is used in the drive control of thestage.
 5. The exposure apparatus according to claim 4, wherein prior toa movement of the stage from the part including the exposure position tothe another part in the first movement area, one head of the three headsused in the drive control of the stage is switched to another head thatis different from the three heads of the four heads, and after theswitching, the positional information measured by three heads that aretwo heads different from the one head among the three heads before theswitching and the another head is used in the drive control of thestage.
 6. The exposure apparatus according to claim 5, wherein thecalibration information is used for the drive control of the stage afterthe switching.
 7. The exposure apparatus according to claim 5, whereinthe plurality of scale plates each have a two-dimensional gratingformed, and are provided at a metrology frame that holds the projectionoptical system, and the plurality of heads are each capable of measuringthe positional information of the stage in both of a direction parallelto the predetermined plane and a direction orthogonal to thepredetermined plane.
 8. The exposure apparatus according to claim 5,further comprising: a detection system having a detection position in asecond movement area different from the first movement area, whichdetects positional information of the object, wherein the encoder systemmeasures the positional information of the stage that is moved in thesecond movement area in a detection operation of the object by thedetection system, by irradiating the measurement beam from below viaeach of the plurality of heads onto another measurement plane that isdifferent from the measurement plane and arranged substantially parallelto the predetermined plane, and the another measurement plane is definedby different plurality of scale plates that are different from theplurality of scale plates and arranged around the detection position. 9.The exposure apparatus according to claim 8, wherein a part of themeasurement plane is an opening, the part including the exposureposition, and a distance between two heads set apart in a firstdirection within the predetermined plane, of the plurality of heads, islarger than a width of the opening in the first direction.
 10. Theexposure apparatus according to claim 9, wherein the stage is moved sothat a plurality of divided areas on the object are each exposed in thefirst movement area, and the distance between the two heads in the firstdirection is larger than a sum of the width of the opening and a widthof one of the plurality of divided areas in the first direction.
 11. Theexposure apparatus according to claim 10, wherein a distance between twoheads set apart in a second direction orthogonal to the first directionwithin the predetermined plane, of the plurality of heads, is largerthan a width of the opening in the second direction.
 12. The exposureapparatus according to claim 11, wherein the stage is moved so that theplurality of divided areas on the object are each exposed in the firstmovement area, and the distance between the two heads in the seconddirection is larger than a sum of the width of the opening and a widthof one of the plurality of divided areas in the second direction. 13.The exposure apparatus according to claim 12, wherein the stage is movedso that scanning exposure of each of the plurality of divided areas onthe object is performed in the first movement area, and in an exposureoperation of the object, a movement of the stage in the first directionfor the scanning exposure and a step movement of the stage in the seconddirection are performed, and the distance between the two heads in thefirst direction is larger than a sum of the width of the opening andtwice a distance of the step movement in the first direction.
 14. Theexposure apparatus according to claim 8, wherein the stage is moved sothat scanning exposure of each of a plurality of divided areas on theobject is performed in the first movement area, and in the another partof the first movement area, a combination of the remaining heads used inmeasurement of the positional information of the stage, of the pluralityof heads, differs depending on a position of the stage, and thecombination of the remaining heads is changed at a time other than ascanning exposure period of the divided area.
 15. The exposure apparatusaccording to claim 14, wherein the combination of the remaining heads ischanged before the scanning exposure of the divided area is started orafter the scanning exposure of the divided area is completed.
 16. Theexposure apparatus according to claim 14, wherein in an exposureoperation of the object, a movement of the stage in the first directionfor the scanning exposure and a step movement of the stage in a seconddirection orthogonal to the first direction within the predeterminedplane are performed, and the combination of the remaining heads ischanged during the step movement.
 17. The exposure apparatus accordingto claim 8, wherein the controller controls the drive of the stage whilecompensating a measurement error of the plurality of heads that occursdue to acceleration of the stage.
 18. The exposure apparatus accordingto claim 8, wherein in the another part of the first movement area, acombination of the remaining heads used in measurement of the positionalinformation of the stage, of the plurality of heads, differs dependingon a position of the stage, and by a change of the combination of theremaining heads according to a movement of the stage, the positionalinformation of the stage is measured using the excluded one head,instead of one of the remaining heads.
 19. The exposure apparatusaccording to claim 18, wherein prior to starting measurement of thepositional information of the stage by the excluded one head, thecontroller decides a measurement value of the excluded one head based onthe positional information of the stage measured by the remaining headsbefore the change of the combination.
 20. The exposure apparatusaccording to claim 19, wherein the combination of the remaining heads ischanged before the stage is moved from the part including the exposureposition to the another part in the first movement area.
 21. A devicemanufacturing method, comprising: exposing an object using the exposureapparatus according to claim 1; and developing the exposed object. 22.An exposure method of exposing an object with an illumination light viaa projection optical system, the method comprising: moving a stage thatholds the object in a first movement area, for an exposure operation ofthe object; measuring positional information of the stage by an encodersystem that irradiates a measurement beam from below via each of aplurality of heads provided at the stage onto a measurement planearranged substantially parallel to a predetermined plane perpendicularto an optical axis of the projection optical system; controlling a driveof the stage based on the positional information measured by the encodersystem; and deciding calibration information of the encoder system basedon the positional information of the stage measured by the encodersystem in a part including an exposure position of the first movementarea, in the exposure position exposure of the object being performedvia the projection optical system, wherein the measurement plane isdefined by a plurality of scale plates which are arranged around theexposure position and on each of which a reflective grating is formed,and in the part including the exposure position of the first movementarea, the positional information of the stage is measured by theplurality of heads that respectively face the plurality of scale plates,and in another part of the first movement area, the positionalinformation of the stage is measured by remaining heads after excludingone head of the plurality of heads.
 23. The exposure method according toclaim 22, wherein in the part including the exposure position of thefirst movement area, the positional information of the stage can bemeasured by four heads of the encoder system, and in the another part ofthe first movement area, the positional information of the stage can bemeasured by three heads of the four heads.
 24. The exposure methodaccording to claim 23, wherein in the another part of the first movementarea, a combination of three heads used in the measurement, of the fourheads, differs depending on a position of the stage.
 25. The exposuremethod according to claim 22, wherein in the part including the exposureposition of the first movement area, the positional information measuredby three heads of four heads of the encoder system is used in drivecontrol of the stage, and in the another part of the first movementarea, the positional information measured by three heads, of the fourheads, having one head different from the three heads used in the partincluding the exposure position is used in the drive control of thestage.
 26. The exposure method according to claim 25, wherein prior to amovement of the stage from the part including the exposure position tothe another part in the first movement area, one head of the three headsused in the drive control of the stage is switched to another head thatis different from the three heads of the four heads, and after theswitching, the positional information measured by three heads that aretwo heads different from the one head among the three heads before theswitching and the another head is used in the drive control of thestage.
 27. The exposure method according to claim 26, wherein thecalibration information is used for the drive control of the stage afterthe switching.
 28. The exposure method according to claim 26, whereinthe plurality of scale plates each have a two-dimensional gratingformed, and are provided at a metrology frame that holds the projectionoptical system, and the plurality of heads each measure the positionalinformation of the stage in both of a direction parallel to thepredetermined plane and a direction orthogonal to the predeterminedplane.
 29. The exposure method according to claim 26, wherein positionalinformation of the object is detected by a detection system having adetection position in a second movement area different from the firstmovement area, and the positional information of the stage that is movedin the second movement area in a detection operation of the object bythe detection system is measured by the encoder system that irradiatesthe measurement beam from below via each of the plurality of heads ontoanother measurement plane that is different from the measurement planeand arranged substantially parallel to the predetermined plane, and theanother measurement plane is defined by different plurality of scaleplates that are different from the plurality of scale plates andarranged around the detection position.
 30. The exposure methodaccording to claim 29, wherein a part of the measurement plane is anopening, the part including the exposure position, and a distancebetween two heads set apart in a first direction within thepredetermined plane, of the plurality of heads, is larger than a widthof the opening in the first direction.
 31. The exposure method accordingto claim 30, wherein the stage is moved so that a plurality of dividedareas on the object are each exposed in the first movement area, and thedistance between the two heads in the first direction is larger than asum of the width of the opening and a width of one of the plurality ofdivided areas in the first direction.
 32. The exposure method accordingto claim 31, wherein a distance between two heads set apart in a seconddirection orthogonal to the first direction within the predeterminedplane, of the plurality of heads, is larger than a width of the openingin the second direction.
 33. The exposure method according to claim 32,wherein the stage is moved so that the plurality of divided areas on theobject are each exposed in the first movement area, and the distancebetween the two heads in the second direction is larger than a sum ofthe width of the opening and a width of one of the plurality of dividedareas in the second direction.
 34. The exposure method according toclaim 33, wherein the stage is moved so that scanning exposure of eachof the plurality of divided areas on the object is performed in thefirst movement area, and in an exposure operation of the object, amovement of the stage in the first direction for the scanning exposureand a step movement of the stage in the second direction are performed,and the distance between the two heads in the first direction is largerthan a sum of the width of the opening and twice a distance of the stepmovement in the first direction.
 35. The exposure method according toclaim 29, wherein the stage is moved so that scanning exposure of eachof a plurality of divided areas on the object is performed in the firstmovement area, and in the another part of the first movement area, acombination of the remaining heads used in measurement of the positionalinformation of the stage, of the plurality of heads, differs dependingon a position of the stage, and the combination of the remaining headsis changed at a time other than a scanning exposure period of thedivided area.
 36. The exposure method according to claim 35, wherein thecombination of the remaining heads is changed before the scanningexposure of the divided area is started or after the scanning exposureof the divided area is completed.
 37. The exposure method according toclaim 35, wherein in an exposure operation of the object, a movement ofthe stage in the first direction for the scanning exposure and a stepmovement of the stage in a second direction orthogonal to the firstdirection within the predetermined plane are performed, and thecombination of the remaining heads is changed during the step movement.38. The exposure method according to claim 29, wherein the drive of thestage is controlled while a measurement error of the plurality of headsthat occurs due to acceleration of the stage is compensated.
 39. Theexposure method according to claim 29, wherein in the another part ofthe first movement area, a combination of the remaining heads used inmeasurement of the positional information of the stage, of the pluralityof heads, differs depending on a position of the stage, and by a changeof the combination of the remaining heads according to a movement of thestage, the positional information of the stage is measured using theexcluded one head, instead of one of the remaining heads.
 40. Theexposure method according to claim 39, wherein prior to startingmeasurement of the positional information of the stage by the excludedone head, a measurement value of the excluded one head is decided basedon the positional information of the stage measured by the remainingheads before the change of the combination.
 41. The exposure methodaccording to claim 40, wherein the combination of the remaining heads ischanged before the stage is moved from the part including the exposureposition to the another part in the first movement area.
 42. A devicemanufacturing method, comprising: exposing an object using the exposuremethod according to claim 22; and developing the exposed object.
 43. Amethod of making an exposure apparatus which exposes an object with anillumination light via a projection optical system, the methodcomprising: providing a stage having a holder configured to hold theobject; providing a driving system having an electromagnetic motor,which drives the stage by the electromagnetic motor, a part of theelectromagnetic motor being provided at the stage; providing an encodersystem having a plurality of heads provided at the stage, which measurespositional information of the stage by irradiating a measurement beamfrom below via each of the plurality of heads onto a measurement planearranged substantially parallel to a predetermined plane perpendicularto an optical axis of the projection optical system; and providing acontroller coupled with the driving system and the encoder system, whichcontrols a drive of the stage based on the measured positionalinformation, wherein the measurement plane is defined by a plurality ofscale plates which are arranged around an exposure position whereexposure of the object is performed via the projection optical systemand on each of which a reflective grating is formed, in a part includingthe exposure position, of a first movement area where the stage is movedin an exposure operation of the object, the encoder system is capable ofmeasuring the positional information of the stage by the plurality ofheads that respectively face the plurality of scale plates, and inanother part of the first movement area, the encoder system is capableof measuring the positional information of the stage by remaining headsafter excluding one head of the plurality of heads, and the controllerdecides calibration information of the encoder system based on thepositional information of the stage measured by the encoder system inthe part including the exposure position of the first movement area.